Answer:
21 feet and 7 inches
Explanation:
I multiplied 6 by 12 twice to find out how many inches she needs for the sides of the ladder which got me 154 then i multiplied 7 by 15 which got me 105 then i added the two products together and got 259 then i divided 259 by 12 to find out how many feet were in 259 inches which got me 21 with a reminder of 7
Therefore, the answer is 21 feet and 7 inches