Answer :

bear with me on this one. start out with 5(3/4)+7(7/8) to get two sides stated in the problem. i then made both an improper fraction, leaving 23/4+63/8 i multiplied them by 2 to get the perimeter. thus 2(23/4)+2(63/8)=23/2+63/4. i multiplied the first term by 1/2 to get them both over 4. 46/4+63/4=109/4. then divide 109 by 4 to get 81.75 which is 81 3/4.
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