In this case we do not know for how long have they worked. But lets assume that they both will fix the car in an hour.
Case 1: Lets talk about Abe first.
Abe will charge $70.00 per hour plus a part which costs $130.00.
Now, the total cost to be paid to Abe to fix the car is [tex]70+130=200[/tex] dollars.
So we will have to pay $200.00 to Abe to fix the car.
Case 2: Lets talk about Gabe now,
Gabe can fix it for $80 an hour and finds the part just for $60.
Now, the total cost to be paid to Gabe to fix the car is [tex]80+40=120[/tex] dollars.
So we will have to pay $120.00 to Gabe.
Considering the two cases above we can ask Gabe to fix our car but there is another case.
Case 3: What if Abe finds a part for $60.00 rather $130.00
In that case, we will have to pay [tex]70+60=130[/tex] dollars in total to Abe.
Now, we need to pay $130.00 to Abe to fix the car.
Still we can see that we need to pay $10.00 less to Gabe so will ask Gabe to fix the car (since [tex]130-120=10[/tex]).