A math problem in the first year of junior high school should have detailed steps

Because of AE Cd, d+ e=180°

The sum of the internal angles of the pentagon is 540°, a+ b+ c+ d+ e=540°, a=130°, c=110°, and d+ e=180°

gives b=120°

Bf cd is used as a parallel line, and the ipsilateral internal angle is complemented by C+ FBC=180; ∠a+∠fba=180.

b=∠fbc+∠fba=70+50=120

Because of the AE CD

So angle e + angle d = 180

Pentagon inner corners and 540

So the angle b = 540-180-130-110 = 120

ae//cd ;So e+ d=180° ; The sum of the internal angles of the pentagonal is (5-2)*180°=540°;

b=540° -a-∠c-∠d-∠e=110° .

Parallel line bf of AE is made at point b

Because bf||ae

So A is complementary to ABF.

So abf=50°

The same goes for fbc=70°

Because ae||The cd is based on two straight rows in parallel

The sum of the internal angles of the pentagon is equal to (5-2)*180 degrees 540 degrees.

From the knowledge of parallel lines, we know that the angle e + angle d = 180 degrees.

So the angle b 120 degrees.

Let a be x degrees.

then its co-angle is 90-x degrees.

The complementary angle is 180-x degrees.

Because the sum of the co-angle of a and the complementary angle of a is a flat angle, then (90-x) + (180-x) = 180

Solution x=45

So a = 45 degrees.

Because A travels 4 hours, B travels 5 hours.

So the first speed is equal to the second speed.

So B has to travel for 5* hours.

If the distance between A and B is divided into 9 parts, A walks 5 9 of the total distance in 5 hours, and 4 9 of the remaining distance in 4 hours. How many hours does it take B to walk 4 9 of the total distance in 5 hours?

B walks 4 9 5 = 4 45 per hour, 5 9 divided by 4 45 = 25 4 hours, that is, the hour, that is, B takes another 6 hours and 15 minutes to reach place A.

Let the small rectangle be a long and a wide b

So 5a = 2b

9a+4b=76

The simultaneous solution is a = 4

b=10, so the small rectangle is 4m long and 10m wide

Solution: Let the length and width of each small rectangle be x and y respectively, which can be obtained from the figure and the title

5x+2x+y）=76

5x=2y is solved by substitution elimination method: x=10, y=4

So the small rectangle is 4m long and 10m wide

The length and width of each small rectangle x, y

2x=5y5y+x+2y)*2=76

2x+14y=5y+14y=19y=76

y=4x=5y/2=10

The length and width of each small rectangle is 10 meters, 4 meters.

Solution: Let the length of the cuboid be y meters. The width is x meters. Since 5x=2y (the top and bottom sides of the large cuboid are equal), then 5x+2y+2x+y+2x+y=76 (the circumference of the large cube is 76) is solved x=4, y=10

1. Set the excess part to x tons.

x = 12 This month's water consumption is 12 + 20 = 32 tons.

2. The question is incomplete. Less. Dad found out a few minutes later that Xiao Ming forgot to bring book 3, and the corner coe and the corner doc were redundant.

Angular AOD = Angular doc, Angular Coe = Angular EOB

Therefore, (angle doc + angle coe) = (angle aod + angle eob) = 180 2 = 90 so mutual congruence.

Do auxiliary lines. There is no picture.

4. Fig. Belch...

5. The angle boc = 30, so the angle con = 15

Angular aob=aAngle AOC = A-30Angular moc = (a-30) 2 angular mon = a 2

1. Use water x tons, x must be greater than 20 tons.

So 20 gives x=32

2, Xiao Ming walked for a few minutes first, don't you know?

3. What about the figure? 1) Angles that are coincident with the angle doc: the angle boe and the angle coe reason: a0b=180°, so eod=90° boe= coe are co-angles.

2) The angle that is complementary to the angle doc has, BOD

Rationale: doc= aod is the way to go.

4. Give the picture.

1 a（108%÷120%）

2. X kWh of electricity is used.

x=3923, motorcycles and trains depart from A and B at the same time, and meet in a few hours40 (45+35)=

1. (1+8%) (1+20%)*100%=90%2.

x=280 electricity fee: 280*yuan).

3. Departing at the same time, how many hours will we meet?

Set x hours to meet.

40/x=45+35x=