56+2n-n+n÷4+3×4=78
56+n + n : 4 + 12 = 78
56+n+n:4 = 78-12 = 66
n+n:4 = 66-56 = 10
4×n + n = 40
5×n = 40 |:5
n = 8
4n÷2+38+3n=58
4n : 2 + 3n = 58 - 38 = 20
4n + 6n = 40
10n = 40 |:10
n = 4
6+3n+n÷3=6×6
3n + n : 3 = 36 - 6 = 30
9n + n = 90
10n = 90 |:10
n = 9