D^2 - 4d = 3d
d^2 - 7d = 0
d(d - 7) = 0
d = 0 or d - 7 = 0
d = 0 or d = 7
.361 .36 .35 1/5
1/5 = .20
Rate = (150 miles)/(3 hrs) = 50 mph
so . . .
(50 mph)*(time) = 400 miles
*divide both sides by 50 mph
time = (400 miles)/(50 mph) = 8 hrs
time = 8 hrs