Answer:
Meryann brought 6 friends to the party
Step-by-step explanation:
y=9x+24
24 is your constant because the cost for all the pizza won't change
9x will change, so x represents the number of friends she brought
and y will be 78 because it's the total amount of money
78=9x+24
all you have to do is solve this equation
54=9x
x=6
