Answer:
Replace all occurrences of y with 6x−3 in each equation.
Replace all occurrences of y in 18x−3y=9 with 6x−3 .
18x−3(6x−3)=9
y=6x−3
Simplify 18x−3(6x−3).
9=9
y=6x−3
Remove any equations from the system that are always true.
y=6x−3
Step-by-step explanation:
<u>Given</u>:
The cost for the children’s party at the rollerskating rink is a function of n, the number of people in the party. The cost function, C is given by

We need to determine the cost to have a party with 9 people and the cost to have a party with 20 people.
<u>Cost of having the party:</u>
From the given function, the cost of having the party for 9 people lies in the interval
Hence, the cost of having the party for 9 people is 150.
Also, from the function, the cost of having the party for 20 people lies in the interval 
Hence, the cost of having the party for 20 people is 260.
1054 (9-8x)=78
(9-8x)= (78÷1054)
9-8x = 0.074
-8x=0.074-9
-8x=-8.926
x= (-8.926÷-8)
x= 1.1157