Let x be the number of chairs in each row.......the total number of chairs = 6x + 2
Note that if he adds 14 chairs to this, he has 8 rows of chairs with the same length
So
[6x + 2] + 14 = 8x simplify
6x + 16 = 8x subtract 6x from both sides
16 = 2x divide both sides by 2
8 = x so .....there are 8 chairs in each row
Proof
6(8) + 16 = 8(8)
48 + 16 = 64