Answer:
n= 5
Steps
4n+5n+15=5n+7n
Subtract n from both sides
4n+5n+15-5n=5n+7n-5n
Simplify
4n+15=7n
Subtract 15 from both sides
4n+15-15=7n-15
Simplify
4n=7n-15
Subtract 7 from both sides
4n-7n=7n-15-7n
Simplify
-3n=-15
Divide both sides by -3
-3n/-3 = -15/-3
Simplify
Answer n=5