For this case we have the following equation:

Let 
We have:

By definition, given an equation of the form 
The quadratic formula, to find the solution can be written as:

In this case we have:

Substituting in the quadratic formula we have:
See attached image
Answer:
Option B
Answer:
$3.75
Step-by-step explanation:
dimes= x
quarters= x+2
nickels= 2x+2
sum is 3.75
.10x+.25(x+2)+0.05(2x+2)=3.75
.10x+.25x+.50+0.10x+0.10=3.75
0.45x=3.15
x=7 dimes (0.70)
x+2=9 quarters (2.25)
2x+2=16 nickels (0.80)
They add to $3.75
Bare with me a minute, I am still trying to figure it out. Here is what I have so far.
If each blue tile has 5 sides and you know you have 3 blue tiles you can multiply 5 by 3
5 x 3 = 15 sides
Next you know the total number of sides is 30 and you just figured out that your 3 blue tiles have a total of 15 sides so you can subtract 15 from 30 to find how many sides are left
30 - 15 = 15sides
Since you know that these are not blue tiles because in the question it stated that you have 3 blue tiles. These have to be sides for red tiles.
Each red tile have 3 sides so you can divide 15 by 3
15/3 = 5
There are 5 red tiles
You are the number 5