There are 6, you'd think there would be 8 but the answer is actually 6. A diagonal is a line segment that connects to vertices, the two vertices chosen do not count when forming the triangle, two vertices that are adjacent to that chosen vertex are NOT included when forming the diagonal. It's confusing, but I hope this helps. If you have any follow up questions I'd love to answer them.
Both of the Billy’s parents (calling the parent billy) being tall is a recessive trait therefore both Billy’s parents has to have at least one recessive trait to make a tall child. Billy’s genotype would be way tt (aka recessive, recessive).
Answer:
C. 
General Formulas and Concepts:
<u>Calculus</u>
- Mean Value Theorem (MVT) - If f is continuous on interval [a, b], then there is a c∈[a, b] such that

- MVT is also Average Value
Step-by-step explanation:
<u>Step 1: Define</u>

f'(c) = 20
Interval [1, b]
<u>Step 2: Check/Identify</u>
Function [1, b] is continuous.
Derivative [1, b] is continuous.
∴ There exists a c∈[1, b] such that 
<u>Step 3: Mean Value Theorem</u>
- Substitute:

- Rewrite:

And we have our final answer!
15 students have roles and 25 do not I hope this is right or at least helps :)