Question

x - y = a. Чему равно 4x - 3y?

Answer 1

x-y=a
x=a+y
y=x-a

4x-3y= 4(a+y)-3y=4a+4y-3y=4a+y

4x-3y=4x-3(x-a)=4x-3x+3a=x+3a