1. 19x+7.8+4.8x-4.9+3y
2. 18y-7y+8.5+y2+9.7

1.
19x + 7.8 + 4.8x - 4.9 + 3y combine like terms
= (19x + 4.8x) + 3y + (7.8 - 4.9)
2.
18y - 7y + 8.5 + y² + 9.7 combine like terms
= y² + (18y - 7y) + (8.5 + 9.7)