Answer:
28
Explanation:
I actually have a fun way of solving these types of problems: replace these key language words with these signs, and let the equation take form: is will become an equal sign, of will become a multiplication sign, and "what number" will become x.
Using the method above, we can simplify the equation to 21 = 75% * x, or 21 = 75%x
75% is the same as 75/100, so now our equation is 21 = 75/100 * x
75/100 simplifies to 3/4, so now our equation is 21 = 3/4 * x
Now we need to isolate the x. Multiplying by the reciprocal of our fraction will convert it to 1x, or just x, which is what we need.
The reciprocal of 3/4 is 4/3, so we multiply both sides by 4/3.
21*4/3 = 28, so x = 28