y = 11. substitute y= 11 into y = 6x + 5
[ 11 = 6x + 5 ]
11 - 5 = 6x (bring 5 over to the left hand side, to subtract from 11)
6 = 6x
6/6 = x (bring 6 over, divide 6 by 6)
1 = x
when y = 17
[17 = 6x + 5]
12 = 6x (take away 5 from left hand side)
2 = x (divide 6 by 12)
