X percent of Y is equal to Y percent of X. So, if you want to find out what 7% of 50 is, you could instead find out what 50% of 7 is, which is 3.5. This means that 7% of 50 is also equal to 3.5.
#41 Use the proper batteries AA goes with AA devices and AAA for the same; okay, in an emergency do the tin foil thing.