Question

How do you solve `5m - 4n = 11` and `3m = n + 15` using substitution?

Answer 1

`m = 7`

`n = 6`

Explanation:

`5m - 4n = 11` ⇒ EQN 1

`3m = n + 15` ⇒ EQN 2

`3m - 15 = n` ⇒EQN 3

Substitute EQN 3 into EQN 1

⇒ `5m - 4*(3m-15) = 11`

⇒ `5m - 12m + 60 = 11`

⇒ `-7m = -49`

⇒ `m = 7`

When `m=7`,

⇒ `3(7) = n + 15`

⇒ `n = 6`

Check if the answers are correctly calculated.

`5(7) - 4(6) = 11` √

`3(7) = 6 + 15` √