Answer :

[tex]7a=3(b-5)\\ 7a=3b-15\\ 3b=7a+15\\ b=\dfrac{7}{3}a+5[/tex]
iGreen
7a = 3(b - 5)

Distribute 3:

7a = 3b - 15

Add 15 to both sides:

7a + 15 = 3b

Divide 3 to both sides:

b = (7a + 15)/3