Respuesta :

let x = miles driven
first plan 0.12x + 57
second plan 0.16x + 46

0.12x + 57 = 0.16x + 46
0.16x - 0.12x = 57 - 46
0.04x = 11
       x = 275

0.12x + 57
= 0.12(275)  + 57 
= 33+57 = 90

answer
a) 275 miles
b) $90