100-71=29
71% lost means 29% remains
you want that 29% to weigh 128lb
so 29% of original=128lb
remember, percent means parts out of 100
x%=x/100 so 29%=29/100
also, 'of' means multiply
29% of original=128
29/100 times original=128
multiply both sides by 100/29
original=12800/29
original=441.37931034482758620689655172414
so about 441lb of apples must be picked
