Rusty has a photograph that is 8 inches wide x 10 inches long. She wants to
enlarge the photograph to make a poster that is 3 feet wide. How long
will the poster be?
the scale ratio is 3'/8"
so, using that ratio on 10", you have
3'/8" * 10" = 3'*(5/4) = 15/4' = 3'9"