Combining Like Terms

Which of these are like terms in the following expression:
3x + 7 - 9x + 24y + 2x²

• 7, 24y
• 3x, 9x
• 3x, -9x
• 3x, -9x, 2x²

-4x - 10x

• -14
• 6x
• -6x
• -14x

Simplify by combining like terms:
5a + 2b - 3a + 4

• 8a + 2b + 4
• 2a + 2b + 4
• 8ab
• 4ab + 4

Simplify the expression: 3x + 2x

• 5x
• x
• 6x
• 5

-6k + 7k=

• k
• -k
• 12k
• -12k

-r -10r

• 11r
• -11r
• 9r
• -11

Simplify the expression: 2x + 1 + 7x 

• 10x
• 10
• 9x + 1
• 9 + 1x

n -10 +9n -3=

• 10n + 13

• 9n - 13

• n

• 10n - 13

Simplify by combining like terms:
5a + 2b - 3a + 4

• 8a + 2b + 4
• 2a + 2b + 4
• 8ab
• 4ab + 4

Simplify by combining like terms:
5a + 2b - 3a + 4

• 8a + 2b + 4
• 2a + 2b + 4
• 8ab
• 4ab + 4