So, Ted wants to make 3 frames. Two sides of each frame are 5 and 3/4 in. long. The other two sides are 7 and 7/8 in. long. Two times three is six, so he needs 6 of each length. I am going to change them into mixed numbers to make them easier to multiply with. So, what we have up to this point is this:
(6)(23/4) + (6)(63/8)=
138/4 + 378/8=
BTW, I am adding them because you are trying to find the total wood lenght. Anyway, so I can't add yet because one has a denominator of 4 and the other has 8. Can't add like that, so I will change it to this:
276/8 +378/8=
654/8=
81 and 3/4 as your final answer