Answer:
or 
Step-by-step explanation:
The formula for finding the any side of the triangle is
We know that a=2 and c=11, so we can go ahead and plug those into the formula.
To find side b, we have to make it alone on one side. Subtract 4 on both side.
Now square root both sides, and that leaves us with:
or
This is a fraction. So it's y over x. So -12 over 9 equals y over -4. After you put those in fractions, you cross multiply. So -12(-4) is 48, and 9y. Then you set them equal to each other, so 48=9y. You divide 9 on both sides and your answer should be y=5.3
We can use a variable equation to solve this. Let A represent alan's age, B represent bob's age, and C represent Cindy's age. So Bob's age would be Alan's age - 5, or a -5 = B. Then Bob's age would be double Cindy's age, so that means 2 multiplied by Cindy's age = Bob's age, or 2C = B. Your two equations are:
A - 5 = B
2C = B
Also a third equation that helps is A + B + C = 20.
Finally, here are the ages.
Alan = 11 years old
Bob = 6 years old
Cindy = 3 years old.
PS: Sorry, I'm not that good at explaining things, but here are the answers
Using an indirect proof:
Assume that the figure is a trapezoid.
All trapezoids are quadrilaterals.
All quadrilaterals' interior angles add up to 360° because any n-gon's interior angles add up to 180(n-2)°.
We are given that the trapezoid has three right angles.
All right angles are 90°, thus these right angles have a total measure of 270°.
We can conclude fourth angle must be 90°.
If it has four right angles, it is a rectangle.
Rectangles have two sets of parallel sides.
However, trapezoids have exactly one set of parallel sides.
Alas, our figure cannot be a trapezoid.
First, let's use the Distributive Property to make our equation easier to solve. Remember that the Distributive Property says the following:
Using this, we can multiply the 7 out to the 
and 3. This gives us:
Now, let's solve for :
We can see that there is one solution for this equation because is equal to one definite value after solving. Thus, our answer is A, one solution.
