A=12 and b=6 a is what percent of b

6 100%
12 x %

x=12*100/6 = 200%

or 
In this case we get at first a decimal as an answer.
A is(=)    what percent(x)      of  (*)     B
12   =       x    * 6
x=12/6= 2
2*100% =200%

When looking at this with just the values, we are trying to find what percent 12 is of 6. We can do this by dividing and multiplying that answer boy 100.
12/6
2•100
200
So, A is 200% of B.

The answer is 90 % because since 20 multiplied by 5 is 100 you would have to do each question multiplied by 5 so 18 times 5 equals ninety percent.