1)7.8а+2.3а-5а при а=6 2)2(0.3b+5)+1,4b при b =4 3)6(а+1.5)-2.8а при а =1.5 4)4(b+0.8)+1.7b при b =2.3.
5.5а-5а=0.5*6=3 0.6б+10+1.4б=2б+10=8+10=18 6а+9-2.8а=3.2а+9=3.2*1.5+9=13.7 4б+3.2+1.7б=5.7б+3.2=5.7*2.3+3.2=16.31