When Fritz drives to work his trip takes 40 minutes but when

When Fritz drives to work his trip takes 40 minutes, but when he takes the train it takes 30 minutes. Find the distance Fritz travels to work if the train travels an average of 15 miles per hour faster than his driving.

Solution

Driving DATA:
time = 2/3 hr ; distance = x miles ; rate = d/t = x/(2/3) = (3x)/2 mph
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Train DATA:
time = 1/2 hr ; distance = x miles ; rate = d/t = x/(1/2) = 2x mph
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Equation:
train rate - drive rate = 15
2x - (3/2)x = 15
(1/2)x = 15
x = 30 miles (distance to work)