Answer:
![\$80.50](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3ega1jarjci0oug341x3znqftsjewwicf1.png)
Explanation:
Let
n ----> represent the number of tickets purchased
y ---> the total cost for a visit to the carnival in dollars
we know that
The linear equation in slope intercept form is equal to
![y=m(n)+b](https://img.qammunity.org/2020/formulas/mathematics/middle-school/nexd7c2mavh7hvrdl38wsm873hixp4fy90.png)
where
m is the slope or unit rate of the linear equation
b is the y-intercept or initial value
In this problem we have
The unit rate or slope is equal to
![m=\$3.50\ per\ ticket](https://img.qammunity.org/2020/formulas/mathematics/middle-school/330mpkvlgirdb8wso568j8s94yt7oue6zb.png)
The y-intercept is equal to the cost for enter (value of y when the value of x is equal to zero)
![b=\$10.50](https://img.qammunity.org/2020/formulas/mathematics/middle-school/az3qk9kq489i8uqpfd2lwh6ebozj4h0tdu.png)
substitute
![y=3.50(n)+10.50](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gmx5ca4f7lh2n9o7lxpqp9h6cbvxhezjwg.png)
For n=20 tickets
substitute the value of n and solve for y
![y=3.50(20)+10.50](https://img.qammunity.org/2020/formulas/mathematics/middle-school/lgt8aj55cbtadqxnp002lk7qxa911daac2.png)
![y=\$80.50](https://img.qammunity.org/2020/formulas/mathematics/middle-school/j45j023xllb3j1hyxyqd2o4m5lpl845fk5.png)