Answer:
n= 5
Step-by-step explanation:
3.5 (10n + 2n-9) = 178.5
Divide 3.5 on both sides
10n + 2n -9 +51
Add like terms to get 12n
12n - 9 = 51
12n = 51 + 9
Add 51 and 9 to get 60
12n + 60
Divide 60 by 12 to get 5
n=5
