1) 5*(4/5)-8*(3/16)= 4-(3/2)=4-1,5=2,5
2) 8х+3у-6х-5у.=8х-6х-5у.+3у=2х-2у
3) m+3-(2m-5)= m+3-2m+5=-m+8
4) 3 1/2 *6/ 7 - 2,25 :9/20 =7/2 *6/7 - 225/100 *20/9 =3 -5 = -2
5) x*(y-t)
8) 4(2,5b-3)-(5b+8).=10b-12-5b-8= 5b-20
9) (20,6-2,4)*2 =18,2*2=36,4 км