x+y=$108,xX80%+yX90%=$90.3.

x+y=$108 ....(1)

xX80%+yX90%=$90.3...(2)

By(1) :

x = 108 - y , sub it to (2) :

(108 - y)(80%) + y(90%) = 90.3

108*0.8 - 0.8y + 0.9y = 90.3

0.1y + 86.4 = 90.3

0.1y = 3.9

y = 39

sub it to (1):

x + 39 = 108

x = 69