Odpowiedź:
a) 7a-1/2a=7•8-1/2•8=56-4=52
b) 3b^2+2b=3•(-4)^2+2•(-4)=3•16-8=48-8=40
c) (2x+3y)(5-x)=(2•2+3(-3))(5-2)=(4-9)•3=-5•3=-15
