Question

Carlos and Maria drove a total of 197 miles in 3.8 hours. Carlos drive the first part of the trip and averaged 55 miles per hour. Maria drove the remainder of the trip and averaged 47 miles per hour. For approximately how many hours did Maria drive?

Answer 1

c=carlos's hour, m=maria
55c+47m=197
c+m=3.8
c=-m+3.8

55(-m+3.8)+47m=197
-55m+209+47m=197
-8m=-12
m=1.5

maria drove 1.5hr or 1 and a half hr.

Answer 2

Hello ! 

Maria : x                                          $55y+47x=197 \\ x+y=3.8 \\ y=3.8-x$
Carlos : y

$55(-x+3.8)+47x=197 \\ -55x+209+47x=197 \\ 209-197=55x-47x \\ 12=8x \\12/8=x \\ 1.5=x \\ \\ Maria drove 1.5 hour or 1 hour 30 minute.$