a) HD Headphones. x=110 x=$70 ea
110×70=$7,700 for HD Headphones
10,000-7,700=2,300 left
y×w=2,300 for basic headphones
My guess, 230 basic headphones for $10 each
b) Basic headphones y×w
55×20=$1,100
2,000-1,100=900
HD Headphones
x×z=900
x=10,z=90 10×90=900
(I'm assuming that the price per item is higher due to the smaller quantity.