Please help me with this problem it is pair each of triangles are similar but not drawn to scale. Calculate any lettered lengths

Problem melissa is her dad build a walkway in their backyard. the walkway will be 54 feet long and 1.5 feet wide. the local hardware store sells tiles which are 1.5 by 1.5 feet and come in boxes of 12. how many boxes of tiles do they need?

Can someone explain to me how to do

1/2+1/6-3/4 simplify the given expression leaving the answer in improper fraction form.