Mark M. answered 03/29/16
Tutor
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Mathematics Teacher - NCLB Highly Qualified
dc + db = 420 sum of distances
7.5(r +30.4) + 7.5(r) = 420 d = r · t
7.5r + 228 + 7.5r = 420 distribute
15r + 228 = 420 combine like terms
15r = 192 subtract 228 from both sides
r = 12.8
The bicycle traveled at 12.8 mph. The car traveled at 43.2 mph.