Question

How do I solve 7? After 7 I think i can do the rest by myself

Answer 1

We have to find the cost of 4 lessons.

The cost for 7 lessons is $82 and the cost for 11 lessons is $122.

We can represent this as 2 points: (7,82) and (11,122).

We can calculate the slope as:

$m=\frac{y_2-y_1}{x_2-x_1}=\frac{122-82}{11-7}=\frac{40}{4}=10$

Then, we can write an equation of a line in slope-point form as:

$\begin{gathered} y-y_1=m(x-x_1) \\ y-82=10(x-7) \\ y=10(x-7)+82 \end{gathered}$

Now we can calculate the cost of 4 classes (x = 4) as:

$y(4)=10(4-7)+82=10(-3)+82=-30+82=52$

Answer: the cost of 4 classes is $52.