Question

A student solved this problem by working backward.

Answer 1

We can also work backwards with this problem. Dale used 3.5+2(5.9)+10=25.3 feet of wood to fix his fence during the day, and was left over with 12.5ft. This means that he started off with 25.3+12.5= 37.8ft of wood at the beginning of the day.

Answer 2

It looks like you have already solved the first question,, so i will help you out with the second one then.
first, you will need to add together all of the used pieces of wood.
3.5 + 5.9 + 5.9 + 10 = 25.3 
now you need to add the 12.5 left over with the amount of used wood that we just found out.
25.3 + 12.5 = 37.8
this means that he had 37.5 feet of wood at the beginning of the day.
let me know if you have any further questions 
:)