first you would convert the fractions into decimals which would be 6 1/2 = 6.5, 2 3/4 = 2.75, 1 5/8 = 1.625, you would then add up the last two decimals, 2.75 + 1.625, which would equal 4.375 and you would subtract that from 6.5 ( 6.5 - 4.375) and get 2.125, so he would be able to give his grandmother 2.125 pounds of apples.