Answer:

Step-by-step explanation:
Given

Required
Find

Calculate 
Using tan rule

So:






'
'So:



4 is the GCF.
Explanation:
4x3=12
4x5=20
5 Isn’t a factor of 12, and 6 isn’t a factor of 20. Each number above doesn’t work, so the greatest common factor of the numbers 12 and 20 must be 4.
Answer:
12
Step-by-step explanation:
Solving the equation would be the easiest way to find out which number fits.
6x - 18 = 54
6x = 72
x = 12