Answer:
The bookkeeper already has a balance of 83.92. She collects 76.75 so that's 83.92+76.75 which equals to 160.67. Then she pays out 38.58 so that's a deduction to what she already has. 160.67-38.58=122.09.
SO the bookkeeper has $122.09 left.
One because the law of consines works on it
Take 20 and divide it by 4 and you get 5mm squared .
There are four sides so take the total which is 20 mm and divide it by the sides to get one side.
Answer is 5mm squared