I like to turn these problems into an equation to solve them.
"12 is what percent of 30" is like saying:
12=x*30
If you know a little algebra, you can solve this by dividing both sides by 30.
.4=x
This is in decimal for however, you must then convert .4 to percent by multiplying by 100 and adding a percent sign:
.4*100=40%
You can sort of check this by thinking. What is 10% of 30? well that is just .1*30 which is 3. Sp since 12 is 4 times your 10% value (3) then the answer is 4 times 10% (40%)! Another way to think about it is 15 is half of 30, which is 50%. 40% is pretty close to 50% and 12 is pretty close to 15. Make sure to add the percent signs where needed, some instructors and math websites will mark you wrong for not having one.
Best of luck!!!
