Question 908841

Algebraic solution
t*(18-12)=3
t*6=3
t=3/6
t=0.5 hours
check
0.5(18-12)=3
0.5(6)=3
3.0=3
ok
3 12 18 0 0
Gaining speed 18-12= 6 mph
Headstart 3 =3 miles
Time to catch up =0.5 hours