Acase of grapefruit weighs 35 and 3/4 pounds. of this weight, 81 is not ripe. what is the weight of the grapefruit that are ripe?

35 + 3/4 = 140/4 + 3/4 = 143/4

7/8 ⋅ 143/4 = 1001/32

1001/32 ≈ 31.28

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So, 

Approximately 31.28 pounds of grapefruits are ripe.

Ican only do part b, sorry : (there is only 1 pound of dark chocolate present because 25% times 3 pounds equals 75% which is the amount of milk chocolate present. 25% times 4 equals 100% which is amount of dark and milk chocolate together.sorry i couldn't do part a.i hope this : )