To find the value of mn, we can use the given equations:

1. 2(m + n) + m - 9 = 0
2. 3m - 3n = 24

First, we can simplify equation (2) by dividing both sides by 3:

3m - 3n = 24

Dividing both sides by 3 gives:

m - n = 8

Now, we can solve equation (1) for m in terms of n:

2(m + n) + m - 9 = 0

Distribute the 2 on the left side:

2m + 2n + m - 9 = 0

Combine like terms:

3m + 2n - 9 = 0

Add 9 to both sides:

3m + 2n = 9

Now, we can use the equation m - n = 8 to express m in terms of n:

m = n + 8

Substitute this expression for m into the equation 3m + 2n = 9:

3(n + 8) + 2n = 9

Distribute the 3 on the left side:

3n + 24 + 2n = 9

Combine like terms:

5n + 24 = 9

Subtract 24 from both sides:

5n = 9 - 24 5n = -15

Now, divide both sides by 5 to find n:

n = -15 / 5 n = -3

Now that we have found n, we can find m using m = n + 8:

m = -3 + 8 m = 5

So, the values of m and n are:

m = 5 n = -3

Now, we can find the value of mn:

mn = 5 * (-3) = -15

Therefore, mn = -15.