Answer:
n = 3
Step-by-step explanation:
start by combining 'like' terms on each side of equation to get:
7n - 9 = -3n + 21
add 3n to each side to get:
10n - 9 = 21
add 9 to each side to get:
10n = 30
n = 30/10 or n = 3
Check:
7(3) - 9 = -3(3) + 21
21 - 9 = -9 + 21
12 = 12
