1) 2x + 3x = (2 + 3) x = 5x
2) 7x - 4x = (7 - 4) x = 3x
3) 3y + 9y = ( 3 + 9)x = 12x
4) 8x + 3x - x = 8x + 3x - 1x = (8 + 3 - 1) x = 10x
5) x + 4x + 5x = 1x + 4x + 5x = (1 + 4 + 5) x = 10x
6) 8x + 3x -x = 8x + 4x - 1x = (8 + 3 - 1) x = 10x
7) 10x + 7x - 8x = (10 + 7 - 8) x = 9x
8) 9y + 2y - 4y = (9 + 2 - 4) y = 7