Question

How do you solve the system of equations `4x + y = 15` and `9x + 3y = 30`?

Answer 1

`x=5, y=-5`

Explanation:

`4x+y=15` --- (i)
`9x+3y=30` --- (ii)

(i) x `3 +`(ii)x`(-1)`
`12x+3y-9x-3y=45-30`
`3x=15`
`x=5`

Substituting `x` into (i)
`4.5+y=15`
`y=15-20`
`y=-5`

Hence,
`x=5, y=-5`