Simplify each expression and find its value when y = 15.(a) 5y - 21 - 2y = (b) 24 + 12y - 9y =

(a) To simplify the expression 5y - 21 - 2y, you first combine like terms.

5y - 2y = 3y

So, the expression simplifies to 3y - 21.

Now, to find its value when y = 15, you substitute 15 for y in the simplified expression:

3(15) - 21 = 45 - 21 = 24

So, 5y - 21 - 2y = 24 when y = 15.

(b) To simplify the expression 24 + 12y - 9y, you first combine like terms.

12y - 9y = 3y

So, the expression simplifies to 24 + 3y.

Now, to find its value when y = 15, you substitute 15 for y in the simplified expression:

24 + 3(15) = 24 + 45 = 69

So, 24 + 12y - 9y = 69 when y = 15.