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How to solve 1200 + 4Y = 500X 2400 + 20x = 20Y
1200+4y=500x
2400+20x=20y
The two formulas are simplified as follows
300+y=125x
120+x=y
If y = 120 + X is taken in, then
300+120+x=125x
x=105/31
Take x into the above equation
y=3825/31
After verification, the answer is correct
（1）1200+4Y=500X （2）2400+20X=20Y
I can't understand one step of your solution because I haven't learned trouble solving
300+120+X=125X
124x = 420? At this step, I didn't understand the 125x above. Why did it become 124x when it was moved down?
Haven't you learned how to merge similar items?
Items of the same kind can be added or subtracted
For example, 300 + 120 + x = 125x
300 and 120 are constant terms. They are of the same type. After merging, they are 420
X on the left and 125x on the right are similar terms, and their coefficients can be added or subtracted
Left to right, symbol changes
125x-x=(125-1)*x=124x
1200+4y=500x 2400+20x=20y
Approximate points
300+y=125x (1)
120+x=y (2)
(2) Substituting (1)
300+120+x=125x
124x=420
x=420÷124≈3.39
Why does 125 become 124? The answer is right
300+120+x=125x
300+120+x-x=125x-x
124x=420
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