18-12/___+6=21

Question

17-5x___+6=8
9-5x___/10+2=9
10+6x___-8=20
8+5x___-6/3=16

Answer 1

since 18-3+6 = 21, I'd say the blank holds a 4, since 12/4 = 3

Do the others in like wise.