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

May 1, 2018

$m = 7$

$n = 6$

#### Explanation:

$5 m - 4 n = 11$ ⇒ EQN 1

$3 m = n + 15$ ⇒ EQN 2

$3 m - 15 = n$ ⇒EQN 3

Substitute EQN 3 into EQN 1

$5 m - 4 \cdot \left(3 m - 15\right) = 11$

$5 m - 12 m + 60 = 11$

$- 7 m = - 49$

$m = 7$

When $m = 7$,

$3 \left(7\right) = n + 15$

$n = 6$

Check if the answers are correctly calculated.

$5 \left(7\right) - 4 \left(6\right) = 11$

$3 \left(7\right) = 6 + 15$