Answer:
3 hours
Step-by-step explanation:
Since the speed is remaining the same, time is proportional to distance, so you have ...
1.75 hours/(70 miles) = (additional hours)/(120 miles)
Multiply by 120 to find the additional hours:
additional hours = (120/70)·(1.75 hours) = 3 hours
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Units of miles cancel from numerator and denominator of (120 miles)/(70 miles).