Question 968710
_________________rate___________time__________distance
firstcar__________r_____________t+k____________d
secondcar_________R______________t_____________d


KNOWN:
r=120
R=135
k=1
UNKNOWN:
t, d, the travel time of second car and the distance when equal for both cars


RT=D relationship gives the system of equations,
{{{system(r(t+k)=d,Rt=d)}}}


Solve the system for t and d.  The question specifically asks for t.  The two formulas for d can simply be equated and then solved for t.