Question

a+3b=15
6(a+4)+3(6b-5)

Answer 1

1)

$a + 3b = 15 \\ a = 15 - 3b \\ a = - 3b + 15$

2)

$6(a + 4) + 3(6b - 5) \\ 6a + 24 + 18b - 15 \\ 6a + 9 + 18b$