First we need to convert the mixed number 2 3/4 into an improper fraction.
To do this, we multiply 2 and 4, add 3 to the product, then we put the sum (11) as the numerator (top number in a fraction) and keep the denominator the same (in this case, 4).
2 3/4 = 11/4.
Now convert the next mixed number yourself.
If you're having trouble, the answer is 1 2/3 = 5/3.
The problem tells us that Harry (sTyLeS) needs 4 pieces of wood that are 2 3/4 ft. in length, and 5 pieces of wood that are 1 2/3.
Since we've already converted the fractions, we can go straight to multiplying. We need to multiply 4 and 11/4, and multiply 5 and 5/3.
The next thing to do is to add the products of our last two calculations.
So your answer would be the second choice. 19 1/3.
I hope this helps you and good luck on your exam!