d+r(t) distance=rate(time) help?

[XxCassyxX]

nick drives into the city to buy software.because of traffic he averages only 15mi/h. on his wat home he averaged 30mi/h. if his total time was 3 hours there and back how long did it take him to get to the store? i really need help i have the answer but i need help with the work

 

[XxCassyxX]

work so far

d1=d2

r(t)=d1 to store
r(t)=d2 back home

15(t)=30(t)

t+t= 3

then im stuck because i don't know if i have it right so far and if i do i don't know the next step

 

[TchrWill]

The distance d is a constant

Then, d/15 + d/30 = 3

Can you take it from here?