Answer: x=10 and y=5
Step-by-step explanation:  Let  be the number of hours worked by the first mechanic.
Let  be the number of hours worked by the second mechanic.
They worked for a combined total of  hours. So we have the following equation.
The first mechanic charged  per hour and worked for  hours.
So, the first mechanic charged  dollars.
The second mechanic charged  per hour and worked for  hours.
So, the second mechanic charged  dollars. 
Together they charged a total of . So we have the following equation.
The two equations above give us a system of linear equations.
We can solve the first equation for .
We then substitute  for  in the second equation to find .