If they sold 89 calendars over 4 weeks, the 'equation' would look like (x = average calendars sold over 4 weeks):

If you solve it, you get:

Which is equal to
22.25. Hope this helps!
Answer:
$52
Step-by-step explanation:
Using the equation
y=mx+c
82=7x+c
122=11x+c
11x-7x=122-82
4x=40
x=10
To get c
82=7(10)+c
82-70=c
c=12
For 4 lessons
y=10(4)+12=52
Adding 1/9 to both sides, we get 2/3+y=8/9. Next, 2/3 can be multiplied by 3/3 to get 6/9 due to that 3*3=9 and using the identity property. We then subtract 6/9 from both sides to get y=2/9
You have to do the opposite
22-17=5
5x3=15
15+13=28
28/4=7
The answer is 7. You can check this by doing what it says and if it makes 22, it’s correct. (I’ve already checked it) :)
You multiply 10 12 times and you will have 1000000000000
than multiply it again by 4.18549 and you will get 418549000000