Part A:
Let x be the number of hours of labor to complete the job
y be the total amount charged.
Since there is an initial charge of $375 for the parts, and $66 per hour, the total amount charged can be written in the equation
[tex]y=66x+375[/tex]Part B:
If James was charged a total of $771, then y = 771, solve for x.
[tex]\begin{gathered} y=66x+375 \\ \\ \text{Substitute }y=771 \\ 771=66x+375 \\ \\ \text{Subtract both sides by }375 \\ 771-375=66x+375-375 \\ 396=66x\cancel{+375-375} \\ 66x=396 \\ \\ \text{Divide both sides by }66 \\ \frac{66x}{66}=\frac{396}{66} \\ \frac{\cancel{66}x}{\cancel{66}}=6 \\ x=6 \end{gathered}[/tex]Therefore, the number of labor hours was 6.