We can create equations to solve this.
2.50p + 1.50m = 29.50
p + m = 15
Solve for a variable in the 2nd equation and use the substitution method to solve.
p + m = 15
Subtract p to both sides:
m = -p + 15
Plug in -p + 15 for m in the first equation.
2.50p + 1.50(-p + 15) = 29.50
Distribute:
2.50p - 1.50p + 22.50 = 29.50
Combine like terms:
p + 22.50 = 29.50
Subtract 22.50 to both sides:
p = 7
Now plug this into any of the two equations and solve for the other variable.
p + m = 15
7 + m = 15
Subtract 7 to both sides:
m = 8
So he purchased 7 pineapples and 8 mangos.
Here is the work and the answer (D=7
Answer:

Minimum 200 people other than the 2 charity representatives.
Step-by-step explanation:
Given that:
The venue can hold a maximum of 500 people.
Cost of venue = $1000
Per person cost for food = $20
Two charity representatives get to attend the dinner for free.
To find:
The inequality and to determine how many people must come to keep costs at most $25.
Solution:
Let the number of people attending the dinner = 
Cost of food for
people = 
Total cost = $1000 + 
Cost per person = Total cost divided by Number of people attending the dinner.
As per question statement:

Therefore, the answer is:
Minimum 200 people other than the 2 charity representatives should attend the dinner.