Answer:
40.90
Step-by-step explanation:
I do not know what pen is but if it is dollars then....
Answer:
2520 patterns
Step-by-step explanation:
In 'n' 10! ways, books can be arranged. But, there are also 5! permutation of blue books 'n1', 2! permutation of identical green books 'n2', and 3! permutation identical black books 'n3'.
Therefore, for non identical arrangements:

= 2520
Therefore, the books can be arranged on a shelf in 2520 patterns
Answer:
I don't know what you mean with a b c d and e, but x=7
Step-by-step explanation:
x=7 because first you subtract 6 from each side, because you wan't to have just x, so you will get 3x=21, and then you just divide both sides by3 to get x=7
Answer:
f(n)= -40.
Step-by-step explanation: