The answer is solved by equations.!!!!

Solution: If two kinds of longan are sold for x kilograms each, then.

120-x=4×（90-x）

Solution. x=80

Therefore, the large longan is left with 120-80 = 40 kg.

Small longan left 90-80 = 10 kg.

Solution: Set two kinds of longan to sell x kilograms.

120-x ＝4（90-x）

120-x＝360-4xx＝80

There are 40 left in the large longan and 10 in the small longan

It's the big longan that sells x so big longan, and there are 120 minus x left and 80 minus x left in the small longan, then it is now 4 times that the big longan is the small longan, that is, 120-x=4 80 minus x, and then solve that x is the amount sold.

Solution: Let the remaining small longan be x kilograms, then the large longan is 4x kilograms.

120-4x=90-x

x=10

Set to sell xkg

120－x＝4x(90－x)

Solve x 80

Large longan: 120 80 40 (kg).

Small longan: 90 80 10 (kg).

Let each sell x

120-x=4（90-x）

4x-x=360-120

3x=240

x=80 Answer: Sell 80 each.

Let the sell be x kilograms.

120-x）=4(90-x)

3x =240

x=80, 120-80=40, 90-80=10

Can you ask the question clearly, who is the pillar?

Large: 40 kg, Small: 10 kg. Thank you.

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120+x=2*(180-x) x=80 Warehouse A shipped 80 tons to warehouse B.

Solution: Warehouse A transported x tons to warehouse B.

180-x/2=120+x

x = 80 A: Warehouse A transported x tons to warehouse B.

Warehouse A transported x tons to warehouse B.

Get: 2(180-x)=120+x

x=80A: Warehouse A transported 80 tons to warehouse B.

The answer at a glance 80 tons were shipped 180-80=100 A leftovers 120 + 80=200 B leftovers.

1. Set up female x people Then male students have (21-x) people.

x-5)*3=21-x

2. Let the elder brother originally save x yuan and the younger brother is x 5

x+20=x/5+100

3. Set X for A, and so is B.

x-31)*4=x-19

4. A x, B (83-x).

x-3=(83-x)*4

If you are new to equations, pay attention to the equivalence relationship in the problem!

If you had the answer, I think you'd be satisfied: -1, -9; One-half plus or minus the root number two, plus or minus one from the seven-thirds below the positive and negative root numbers, plus or minus two times the root number five from the three-quarters, no solution, -2 and 6

When x = 10, that is, the price is 280, the average daily sales profit can reach 720 yuan.

(1) First, you have to be clear that if you don't reduce the price, your profit per ton is 40 yuan, and now the price is reduced by x yuan, y = 40-x

2) Solution: Let the price of cement per ton be reduced by X yuan now, profit = sales volume * profit per ton.

Column: [16 + (x 5) * 4] (40-x) = 720 x = 10, so the actual sales price of no ton of cement is positioned at 280 yuan.

Solution: Let the speed of the water flow be x kilometers per hour.

26+x)×3=(26-x)×(3+

78+3x=

3x+x=13÷x=2

Solution: If the unit price of basketball is X yuan, then the unit price of volleyball is X-8 yuan 4x+5 (x-8) = 185

4x+5x-40=185

9x=185+40

x=225÷9

x=25 volleyball: 25-8=17 yuan.