a Since we are given time, distance, and speeds, we can use the d=rt formula in order to right an equality.
d=rt
The given distance is equal to 135 miles. The rate is equal to 55 mph on highways and 40 mph on the rest of the roads. If we let x represent the time we spend on the highways and y represent the time we spend on the rest of the roads, we can complete the equation.
55x+40y=135
Note that the time we spend on the highways and the time we spend on the rest of the roads sum up to 3 hours.
x+y=3
If we combine the above equations we can form a system of equations.
55x+40y=135 & (I) x+y=3 & (II)
In order to solve it we will use the Substitution Method.
