Question

How do you solve `x + y = 12`,`y =2x` using substitution?

Answer 1

`x=4 and y=8`

Explanation:

`x+y = 12 -> y=12-x`
`y=2x`
which means `12-x=2x -> 3x=12 -> x=4`
replace x in one of the equations above, for exemple the 2nd :
`y=2*4=8`