A pile of coal, the factory originally planned to burn 60 days, 15 tons a day, the actual daily savings of 20% than the original plan, this batch of coal actually burned how many days?

A pile of coal, the factory originally planned to burn 60 days, 15 tons a day, the actual daily savings of 20% than the original plan, this batch of coal actually burned how many days?

60 × 15 = 900 (tons); 15 × (1-20%) = 12 (tons); 900 ／ 12 = 75 (days). Answer: this batch of coal actually burned for 75 days

A pile of coal, originally planned to burn 3 tons per day, can be burned in 26 days. Now save 0.4 tons per day, how many days can be burned?

Suppose you can burn for X days
（3-0.4）x=3*26
2.6x=78
x=78÷2.6
x=30

A pile of coal, originally planned to burn 4 tons per day, can burn 72 days. Due to the reconstruction of the stove, saving 0.8 tons per day, how many days can this pile of coal burn

72 * 4 / (4-0.8) = 90 days

A batch of coal, originally planned to burn 15 tons per day, can burn 60 days, the actual daily coal saving than the original plan 1 / 5, how many days does this batch of coal actually burn?

The method is simple
60÷（1-1/5）
=60÷4/5
=75 days

The method of addition, subtraction and elimination is used to solve the equations

x/3+y/4=1 ...(1)
x/3-y/2=1 ...(2)
(1) (2) eliminate X
So y / 4-y / 2 = 1-1 = 0
y=0
Then x = 3

{x + Y / 2 + X-Y / 3 = 64 (x + y) - 3 (X-Y) = 0} the equations are solved by addition subtraction elimination method

(x+y)/2+(x-y)/3=6…… ①4(x+y)-3(x-y)=0 …… ② From ①: 3 (x + y) + 2 (X-Y) = 363x + 3Y + 2x-2y = 365x + y = 36 ③ From ②: 4x + 4y-3x + 3Y = 0x + 7Y = 0 ④ 4 × 5 - 3: 5x + 35y - (5x + y) = 0-3634y = - 36Y = - 18 / 17 bring y = - 18 / 17 into 4 x = 0-7y = 0 - [7 × (...)

Solve the equations: x + 13 = 2Y2 (x + 1) − y = 11

Solution (1): get x = 6y − 12x − y = 9 from the original equations, substitute ① into ② to get 2 (6y-1) - y = 9, that is, y = 1; substitute ① to get x = 5; the solution of the original equations is x = 5Y = 1. Solution (2): get x + 1 = 6y from x + 13 = 2Y, and substitute ① into 2 (x + 1) - y = 11 to get 12y-y = 11, that is, y = 1; substitute y = 1 into ① to get x = 5; the solution of the original equations is x = 5Y = 1

Please make up an applied problem with the equations {X-Y = 5, {3x + 2Y = 30

There are five more big monks than little monks in a temple. One day, they ate 30 steamed buns at noon. It is known that the big monk ate three and the little monk ate two. How many big monks and little monks are there in this temple

According to the equations 2x + 4Y = 36,3x + 2Y = 36, write an application problem

It costs 36 yuan to buy two pens and four pencils, while it costs 36 yuan to buy three pens and two pencils. How much are the pens and pencils?

2 3 4 5 6 7 8 9 = 10 can't multiply and divide, can only add and subtract, can't use bracket

You're kidding!
Note: 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 = 45
If only the addition and subtraction needs to leave 10, then there are 35 to offset each other, so there must be 17.5-17.5 to complete. This is obviously impossible!
But there is a case that numbers can be combined in pairs (without a sign in the middle) as a two digit number
12+3+45-67+8+9=10