Step-by-step explanation:
the slower truck travels x miles in 5 hours.
the faster truck travels x + 5×2 = x + 10 miles in 5 hours.
so,
x + x + 10 = 315 miles
2x = 305 miles
x = 152.5 miles (in 5 hours)
therefore, the slower truck's speed was 30.5 mph.
the faster truck's speed was 30.5 + 2 = 32.5 mph.