Question

how to solve 4y=x 3x- y=70 using substitution

Answer 1

x = 4y
3x - y = 70

substitute the x in the second equation with the other half of the first equation.

3(4y) - y = 70
12y - y = 70
11y = 70
y = 6.36 repeating, or 6 4/11

now use this to solve first equation
x = 4 (6 4/11)
x = 25.45 repeating

done