Direct variation is of the form y=kx, where k is the constant of variation.
In this case we are given a point (1/2, 2/3) so we can solve for k.
2/3=k/2 multiply both sides by 2
4/3=k, so our equation is:
y=4x/3, so when y=8
8=4x/3 multiply both sides by 3
24=4x divide both sides by 4
6=x
