1) Simplify the expression: 3x + 2x - 5x Solution: 3x + 2x - 5x = (3 + 2 - 5)x = 0x = 0

2) Simplify the expression: 4y - 2y + 7y Solution: 4y - 2y + 7y = (4 - 2 + 7)y = 9y

3) Simplify the expression: 2a + 3b - a + 4b Solution: 2a + 3b - a + 4b = (2 - 1)a + (3 + 4)b = a + 7b

4) Simplify the expression: 5m - 3n + 2m + 4n Solution: 5m - 3n + 2m + 4n = (5 + 2)m + (-3 + 4)n = 7m + n

5) Simplify the expression: 6x - 2y + 3x + 5y Solution: 6x - 2y + 3x + 5y = (6 + 3)x + (-2 + 5)y = 9x + 3y