15-b=4b-5(5-3)
Multiply the bracket by -5
(-5)(5)=-25
(-5)(-3)=15
15-b=4b-25+15
15-b=4b-10
Move 15 to the other side
Sign changes from +15 to -15
15-15-b=4b-10-15
-b=4b-25
Move 4b to the other side.
-b-4b=4b-4b-25
-b-4b=-25
-5b=-25
divide both sides by -5
-5b/-5=-25/-5
Answer: b=5