Question

A blue car passes a red car on the freeway at a relative speed of 12 mph. At the same time, a green car is traveling at 57 mph in the opposite direction. The green passes the red car with a relative speed of 126 mph. What is the speed of the blue car?

Answer 1

\[v_{b,r}=v_b-v_r=12 mph \] \[v_{g,r}=v_g-v_r=126 mph \] \[v_g=57 mph \]

Answer 2

not so sure, mate

Answer 3

just tweak them