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Let t= number of units of time needed for the road call
Now we know that it would be more economical to use Rick's if the total cost of the road call is less than Twin City
So our equation to solve is:
50+15t<70+10t subtract 10t and also 50 from both sides
50-50+15t-10t<70-50+10t-10t collect like terms
5t<20 divide both sides by 5
t<4 units of time, in other words, if the road call takes less than an hour it would be more economical to use Rick's
Clearly, if t=4 units of time, then the two would cost the same
50+60=70+40
110=110
Hope this helps------ptaylor
