350 miles
1) Let's set those two equations:
1st plan:
73.98+0.09x 0.09x because that 0.09 depends on how many miles are driven
2nd plan:
59.98 +0.13x 0.13x because that 0.13 depends on how many miles are driven
2) We need now to equate those two equations so that we can find out how many miles
73.98 +0.09x = 59.98+0.13x Subtract 0.09x from both sides
73.98 = 59.98 +0.13x -0.09x Subtract 59.98 from both sides
73.98 -59.98 = 0.04x
14= 0.04x Divide both sides by 0.04
x =350
3) Hence, driving 350 miles won't matter choosing the 1st or the 2nd plan.