20. If a motorist had driven 1 hour longer on a certain day and at an average rate of 5 miles per hour faster, he would have covered 70 more miles than he actually did. How many more miles would he have covered than he actually did if he had driven 2 hours longer and at an average rate of 10 miles per hour faster on that day?
any ideas on how to set up an equation?
original: time = t, rate = r and distance = d = tr
after change: time = t+1, rate = r+5 and distance, d +70 = (t+1)(r+5)
d +70 = tr + 5t + r+5
70 = 5t + r+5
after change again: time = t+2, rate = r+10 and distance, d +x = (t+2)(r+10)
d +x = tr + 10t +2r+20
d +x = d + 10t +2r+10+ 10
x = 2 (5t +r+5) + 10
x = 2x70 + 10
x = 150