bsically, you subsitute and multiply
c=75+15n
a
for 3 people
subsitute 3 for n
c=75+15(3)
c=75+45
c=120
cost for 3 people is 120
B
1 person
c=75+15(1)
c=75+15
c=90
cost for 1 person is 90
C
15 poepls is
c=75+15(15)
c=75+225
c=300
300 people for 15 people
D
so if cost is 165
c=165
165=75+15n
subtract 75 from both sides
90=15n
divide by 15
6=n
6 people
the answers:
a.$120
b.$90
c.$300
d. 6 people