Question

Find the value of y when x equals 4.
-3x + 9y = -57

Answer 1

y = -5

Explanation:

Isolate y:

-3x + 9y = -57

9y = -57 + 3x

y = (-57/9) + (3/9)x

Substitute for x:

y = (-57/9) + (3/9)(4)

y = (-57/9) + (12/9)

y = (-45/9)

y = -5

Answer 2

`\mathsf {y = -5}`

Explanation:

`\textsf {Given :}\\\textsf {-3x + 9y = -57}`

`\textsf {Divide throughout by 3 :}`

`\mathsf {(1)/(3) * (-3x + 9y) = (1)/(3) * -57}`

`\mathsf {-x + 3y = -19}`

`\textsf {Substitute x = 4 :}`

`\mathsf {-(4) + 3y = -19}`

`\mathsf {3y = -15}`

`\textsf {Divide by 3 on both sides :}`

`\mathsf {(3y)/(3) = (-15)/(3) }`

`\mathsf {y = -5}`