1) 8х + 21х = ( 8 + 21 )х = 29х;
2) 78а - 49а = ( 78 - 49 )а = 29а;
3) 326у + 99у = ( 326 + 99 )у = 425у;
4) 15,3х - 8,8х = ( 15,3 - 8,8 )х = 6,5х;
5) 9,8b + b = 9,8b + 1b = ( 9,8 + 1 )b = 10,8b;
6) 20,6m - m = 20,6m - 1m = ( 20,6 - 1 )m = 19,6m;
7) 31t - 9,1t = ( 31 - 9,1 )t = 21,9t;
8) 2y + 19y + y = 2y + 19y + 1y = ( 2 + 19 + 1 )y = 22y;
9) 6х - 5х + х = 6х - 5х + 1х = ( 6 - 5 + 1 )х = 2х;
10) 7b + b - 8b = 7b + 1b - 8b = ( 7 + 1 - 8 )b = 0b = 0.