I need to know if the following pairs of expressions are equivalent!

10a - 7a and 5a + 2a - 4a

9 - 4y and 4y - 9

6 + s and 6s

2c + 6c + 9 - c - 4 and 7c + 5

Step-by-step explanation:

1) 10a - 7a = 3a {10a & 7a are like terms. So we can subtract}

5a + 2a - 4a = 7a - 4a = 3a {5a, 2a, 4a are like tems}

So, 10a - 7a and 5a + 2a - 4a are equivalent expressions

2) 9 - 4y and 4y - 9 are not equivalent

3) 6 + s means 6 is added to s

6s means 6 is multiplied by s.

6 + s and 6s are not equivalent expressions

4) 2c + 6c + 9 - c - 4 = 2c + 6c - c + 9 - 4

= 8c - c + 5

= 7c + 5

7c + 5

2c + 6c + 9 - c - 4 and 7c + 5 are equivalent expressions