The second one seems about right.
Answer=7:13
Kenny's Weight*6/7=Melvin's Weight
So, for example, if Melvin's weigh was 7...
Kenny's Weight*6/7=7
divide both sides by 6/7
Kenny Weight=6
So we can say that Melvin's weight to Kenny's weight is 7:6
The boys total weights would be...
7+6=13
So Melvin's weight over the total weight of the two boys is:
7:13
You might need a maths degree for this one, I believe it’s 4 but don’t quote me on that.
2x-6y=24
-5x+6y=-6
2x=24+6y
2x-24=6y
-5x+6y=-6
6y=5x-6
2x-24=5x-6
-24+6=5x-2x
-18=3x
-18/3=x
x=-6
2x-6y=24
2(-6)-6y=24
-12-6y=24
-6y=24+12
-6y=36
y=36/-6
y=-6
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)