Let's do the easy part first. You can get three 12.5 inch background blocks out of each width of fabric, so you need 35/3 lengths or roughly 12 lengths of 12.5 inches each. or 150 inches of width divided by 36 = just over 4 yards for the background blocks. But, since you d didn't use the ends of each strip, you can have a strip about 150 inches long and 6 inches wide which is plenty big enough to cut the squares you need for the lily blocks. You can get 2 of the 4.5 x17 inch strips from one width of fabric, with some left over. So generously you need 18 times 4.5 or 81 inches of fabric which is 2.25 yards. So for the background fabric you need 6.25 yards.
For the pink, you can get 2 of the 2.5 inch strips from each width, so 18 times 2.5 is 45 inches or 1,25 yards.
For the green you can cut at least 8 squares from each width. So you need
35/8 lengths (35/8=4.37 round up to 5 times 5 inches or 25 inches in length or less than 3/4 of a yard.
But that doesn't count the borders. Without any idea of how big those border triangles are I can't imagine how you figure yardage.
A quilt of 7 X 5 blocks will be about 120 X 85 before you add borders. Did you want it to be so big? That's 8 yards of backing if you cut it horizontally. But remember that doesn't count borders.
Linda F. Apex,. NC