Answer:
23
Step-by-step explanation:
they add five
9+5=14
12+5=17
15+5=20
18+5=23
I think it’s 10,21 and 40, in that order. Sorry if I’m wrong:(
Answer:
Thank you
Step-by-step explanation:


When

, you're left with

When

or

, you're left with

Adding the two equations together gives

, or

. Subtracting them gives

,

.
Now, you have



By just examining the leading and lagging (first and last) terms that would be obtained by expanding the right side, and matching these with the terms on the left side, you would see that

and

. These alone tell you that you must have

and

.
So the partial fraction decomposition is
On the 1st place he can put 6 textbooks, on the 2nd 5 textbooks etc...
6 · 5 · 4 · 3 = 360
Answer: D) He can arrange textbooks in 360 ways.