Answer:
168 minutes, or 2 hours, 48 minutes
Explanation:
Set up a proportion and solve.
56 minutes is to 4 tires as 'x' minutes are to 12 tires
becomes
56/4 = x/12 solve for x...
[56(12)]/4 = x (multiply both sides by 12 to get rid of the fraction)
672/4 = x (simplify 52(12) = 672)
168 = x (simplify 672/4 = 168)