Divide 5 by 4 and the left over Is the top of the fraction then your divisor is on the bottom so it would be 1 and 4/5.
Think of this, 77/100 is 0.77. 0.77 is 77%.
Just use this for the rest of the questions.
A(6) and D(-4) are solutions to the equations
(6)^2 < 81 | 36 < 81
(-4)^2 < 81 | 16 < 81
Check the picture below, that's just an example of a parabola opening upwards.
so the cost equation C(b), which is a quadratic with a positive leading term's coefficient, has the graph of a parabola like the one in the picture, so the cost goes down and down and down, reaches the vertex or namely the minimum, and then goes back up.
bearing in mind that the quantity will be on the x-axis and the cost amount is over the y-axis, what are the coordinates of the vertex of this parabola? namely, at what cost for how many bats?

![\bf \left( -\cfrac{-7.2}{2(0.06)}~~,~~390-\cfrac{(-7.2)^2}{4(0.06)} \right)\implies (60~~,~~390-216) \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ ~\hfill (\stackrel{\textit{number of bats}}{60}~~,~~\stackrel{\textit{total cost}}{174})~\hfill](https://tex.z-dn.net/?f=%5Cbf%20%5Cleft%28%20-%5Ccfrac%7B-7.2%7D%7B2%280.06%29%7D~~%2C~~390-%5Ccfrac%7B%28-7.2%29%5E2%7D%7B4%280.06%29%7D%20%5Cright%29%5Cimplies%20%2860~~%2C~~390-216%29%20%5C%5C%5C%5C%5B-0.35em%5D%20%5Crule%7B34em%7D%7B0.25pt%7D%5C%5C%5C%5C%20~%5Chfill%20%28%5Cstackrel%7B%5Ctextit%7Bnumber%20of%20bats%7D%7D%7B60%7D~~%2C~~%5Cstackrel%7B%5Ctextit%7Btotal%20cost%7D%7D%7B174%7D%29~%5Chfill)
You should plug this into a graphing calculator on your computer! It helps a lot!