Y = x^2 + 8x - 3
y = x^2 + 8x + (8/2)^2 - 3 - (8/2)^2
y = x^2 + 8x + 16 - 3 - 16
We are given :

Step 1: factor the part inside square root
The function given inside square root is of quadratic form.
So let us try to factorise it using AC method.
Here A*C = 4*25 = 100
so we have to find factors of 100 that add up to give -20.
the two factors are -10 and -10.
Rewriting the function :

=
=
=
Step 2:
Now we take square root of the factorised form

= 
Answer : (2x-5)
Y=55x+200, you multiply the number of weeks by the amount of money, and add 200 because they started with that.
13 red, 5 blue, 7 green...for a total of 25
percentage of green ones is : 7/25 = 0.28 = 28% <==