First

Then

To get

So...


To get y = 4.


Next

Finally

Therefore our solutions are y = 4, x = 3
You can go full 2π rotate around counterclockwise so the angle wouldn't be negative.
So -π/2 + 2π = -π/2 + 4π/2 = 3π/2
So (4, 3π/2) is the same point as (4, -π/2)
Answer:
$3.05
Step-by-step explanation:
Backpack=$18.70
6 note books=x
Sales tax=6%
Total cost=$39.22
18.70+x+0.06(18.70+x)=39.22
18.70+x+1.122+0.06x=39.22
19.822+1.06x=39.22
1.06x=39.22-19.822
1.06x=19.398
x=19.398/1.06
=18.3
x=$18.3
6 books=$18.3
Each book cost=18.3/6
=$3.05