Help with this substitution

Since x = 3y + 15, plug that into the other equation.

5x + 2y = 7
5(3y + 15) + 2y = 7
15y + 75 + 2y = 7
17y = 7-75
17y = -68
y = -4

I hope this helps. (x = 3 and y = -4)

Suredude why not right

At a constant it will take one hour to travel 32 mi.at that speed it will take 1/2 hr to travel the remaining 16 mi.it will take 1+1/2 hr to travel the 48mi @ 32mph.so 1 hr = 60 min& 1/2 hr = 30 min1+1/2 hr = 90 min.there are 60s in each 90 × 60 = 3600 seconds.the real question seriously is he why are they driving so slow? ! lol.