Chris got 60 mph: https://web2.0calc.com/questions/3-questions-on-algebra
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It takes Tina 30miles / 45mph = 2/3 of an hour to get to work = 40 minutes
So......10 minutes earlier is 30 minutes.....so........to travel 30 miles in 30 minutes....she must travel at 1 mile per minute = 60 mph "