Question

How do you solve `4x + 5y = 18` and `x = 39 -7y` using substitution?

Answer 1

`y=6`
`x=-3`

Explanation:

`4x+5y=18` -----1
`x=39-7y`-----2

subtitute equation 2 into equation 1

`4(39-7y)+5y=18`
`156-28y+5y=18`
`156-23y=18`
`-23y=-138`
`y=6`

subtitute `y=6` into equation 2

`x=39-7(6)`
`x=-3`