dKathy and Brian drove a total of 750 miles in 12 hours. Kathy drove 65 miles per hour and Brian drove at 55 miles per hour. For what length of the time did Kathy and Brian drive

Answer 1

65K + 55B = 750

K+B = 12

multiply by 55 in order to eliminate one variable

55K + 55B = 55(12) = 660

subtract this from the 1st equation to get

65K - 55K = 10 K = 750-660 = 90

K = 90/10 = 9 hours drive for Kathy

B = 12-9 = 3 hours drive for Brian

55(3) + 65(9) = 165 + 585 = 750 miles total

they both drove 3 and 9 hours each. 3+9=12 hours total