Elimination by Addition and Subtraction - Examples & Practice

Justin just graduated from college and is deciding which job offer to take. He plans to work $h$ hours per month. After his monthly spending, he is left with $s$ dollars left over for possible savings. $$\begin{array}{lrcl} \text{Job Offer A: }&s&=&20h-1800 \\ \text{Job Offer B:}&s&=&10h-800 \end{array}$$ How many hours per month would he have to work to get the same amount of dollars left over from each job?