Answer:
Step-by-step explanation:
I am sorry but please give detailed question
Answer:

Step-by-step explanation:
The given ratio is 
9 is the common factor of 18 and 27
divide numerator and denominator by 9

hence
is proportion with 
So the equation looks like this : 15*3x=78
subtract 15 from both sides: -15 -15
then divide by 3 from both sides
to isolate the variable: 3x=63
3/3x=63/3
x=21 (your mystery number is 21)
Answer:
186 books with the 55% increase
Step-by-step explanation:
120 times 55% increase = 66 more in increase
Now take the increase and add it to the original amount of books to get the number of books with the increase
66 + 120 = 186