16. the admission to a local fair is $10 for each adult and $6 for each child. each ride cost $1.50 for an adult and $1 for a child.

a. write an expression that represents how much more adult will spend at the fair.

b. an adult and child each go on 7 rides. how much more did the adult spend?

Let x = number of adults let y = number of children 
There are 30 people in the group, so x+y = 30 
The total cost is $175, so 10x + 5y = 175 
10x + 5y = 175 Divide by 5: 2x + y = 35 
Now subtract the two equations: 2x + y = 35 x + y = 30 x = 5 
Substitute x into one of the equations to find y. 
5 + y = 30 y = 25 
Now plug both values into the other equation to check your work. 
2(5) + 25 = 35 10 + 25 = 35 35 = 35

Main idea on left, details on right