Beer? at an electronic store? but srsly, 81*.07 is 5.67, total is 86.67
Let's call the number you thought of n. Then what the two steps you took can be written as an equation:

Subtract n to get all of your variables to one side:

At this point, I recommend turning your mixed number into an improper fraction. It will make things easier later on:

Now divide both sides by 11 to get the value of n:
<h2>
QUESTION</h2>
What is 33% of 400?
<h2>
ANSWER AND EXPLANATION</h2>
To find the percent of a number, you have to change the percent into a decimal or a fraction and multiply by the number.
<h3>
DECIMAL</h3>
To change a percent into a decimal, remove the percent sign and move the decimal point 2 places to the left.

Now that you have your decimal, multiply by 400:

ANSWER = 132
<h3>
FRACTION</h3>
To change a percent into a fraction, make the percent number as the numerator(top number) and 100 as the denominator(bottom number) since fractions are out of 100.

Now that you have your fraction, multiply by 400:

ANSWER = 132
<em>If you have any questions, feel free to ask in the comments! :)</em>