Question 101832
12 lbs is to 1.5 inches as 64 lbs is to X inches. Assuming the 64 lbs didn’t break the spring, then you can set up a ratio. 
{{{12/1.5 = 64/X}}}
{{{X*(12/1.5) = X*64/X}}} Multiply both side by X.
{{{X*(12/1.5) = 64}}} Simplify
{{{X*(12/1.5)*(1.5/12) = 64*1.5/12}}} Multiply both side by (1.5/12)
X = 8 inches