Jamal was riding his bike home at a speed of 12 mph. On his trip out, he had traveled 8 miles away from his house. He has been traveling for a half hour at this speed.

How far away from home is he?

Question

Jamal was riding his bike home at a speed of 12 mph. On his trip out, he had traveled 8 miles away from his house. He has been traveling for a half hour at this speed.

How far away from home is he?

anonymous · Answer

suppose hishouse is at the position x0=0, he starts travelling back from x=8, his speed is 12mph and the time is 0.5hours... so:
$$x=x0-vt=8-12\times 0.5$$
note the negative sign for the velocity, sinde he is going in the negative direction, from point 8 to point 0