Question

How do you solve `x-y=3` and `7x-y=-3` using substitution?

Answer 1

`x = -1 and y = -4`

Explanation:

Another method which will work well in this case is to equate two equal expressions. This is a form of substitution.

Transpose both equations to give `y = ...........`

equ 1. `y = x - 3" and "` equ 2. `y = 7x + 3`

Note that `" " y = y`

Therefore: `7x + 3 = x - 3`
`" " 6x = -6`
`" "x = -1`

Equ 1. `y = -1 -3 rArr y = -4`