Star with the statement: "Given that the sum is 11"
which may seem a bit odd considering its the last part of the problem
The "given" is important as it sets up the constraints of what we're dealing with. In this case, we know 100% (we can see or someone told us without lying) that the sum is 11. We don't know what the individual values are but we know they add to 11.
What are the ways to add to 11? Well they are...
5+6 = 11
6+5 = 11
so there are 2 ways to do it. As you can see, none of those ways involve a double. A double is where we have two of the same values (eg: snake eyes which is 1 and 1 giving 1+1 = 2 as the sum). It turns out that it's impossible to have doubles add to any odd number.
So if we know the sum is 11, and we're asking "what is the probability of rolling doubles", then the answer is 0.
The 0 indicates "impossible" or "certainty of it never happening".
To solve this problem you must apply the proccedure shown below:
1. You have the following expression given in the problem above:

2. The first thing you must do to factor the expression is to group the terms, as following:

3. Now, choose the greatest common factor of each group:

4. Now, you need to factor the expression by factoring out the 

The answer is: 
A=3+(s/2)
a=206
206=3+(s/2)
minus 3 both sides
203=s/2
times 2/1 both sides
406=s
sabrina=406
to check
206=3+(406/2)
206=3+(203)
206=206
true
Answer: (0,-4)
You solve this with inverseoperations
You do 6.394-3.200 which =
3.194