Пошаговое объяснение:
1) 10a+b-10b-a = 9а-9b
2)-8y+7x+6y+7x =-2y+14x
3)-8x+5.2a+3x+5a =-5x+10.2a
4)5a+7a-9.2m+15m = 12a+17.8m
5)2/7x-4/9y-5/14x+2/3y=4/14x -4/9y-5/14x+6/9y=-1/14x+2/9y
