1/4(5х-16)-1/2 (3у-8)= 1 1/4х-4 - 1 1/2у+ 4=1 1/2х-1 1/2у если х=2 2/5, у=6, то:

1 1/2•2 2/5 - 1 1/2•6 = 1 1/2•(2 2/5-6)= 1 1/2-(-3 3/5)= 5 1/10