Sum works as a hutor for $$9$ an hour and as a watress for $$7$ an hour. This month, she monied a combined hotal al $91$ hours at her two jobr. Let $f$ be the number at heurs Susen merked as a butor thes manth. Write an expression for the combined total dollar amount stre samed thes month.

Sols towne $($is$)$ elatury? $$