5) ...=6a-2ab-3ab+6b-5ab-5a-5b=a-10ab+b
при a=1,5, b= -2,6
1,5 +10*1,5*2,6-2,6=37,9
6) .....= -5/8*56/10 m +5/8*16/10 n - 72/10*4/9 m - 72/10*25/18 n= -3,5m+n - 3,2m - 10n= -6,7m - 9n
при m=10, n=5/18
-6,7*10 - 9*5/18=-67-2,5=-69,5
7) ...= -0,9x-2y-0,6x-0,5y= -1,5x - 2,5y
при x= - 1 1/3, y=1,2
15/10*4/3 - 2,5*1,2=2-3= -1
8) ....=a - 2/3 b -3a+0,3b= -2a -11/30 b
при. a=5,5, b=2 8/11
-2*5,5 - 11/30*30/11= -11 - 1= -12