Two mechanics worked on a car. the first mechanic worked for 20 hours, and the second mechanic worked for 15 hours. together they charged a total of $1775 . what was the rate charged per hour by each mechanic if the sum of the two rates was $100 per hour?

For this case we have the following variables:
 x = amount of $ / hr that the mechanic obtains 1.
 y = amount of $ / hr obtained by mechanic 2.
 We write the system of equations:
 x + y = 100
 20x + 15y = 1775
 Solving the system of equations we have:
 x = 55 $ / hr
 y = 45 $ / hr
 
 the rate charged per hour by each mechanic was:
 x = 55 $ / hr
 y = 45 $ / hr

Ithink your answer is b