Answer: Symmetric property of equality
This is the idea that if x = y, then y = x. We can swap the left and right sides of an equation, and still mean the same thing. The same applies to congruences as well.
The answer to the first question would be 1% of the purchase price and the answer to the second question would be 0.5 % of the purchase price.
120 / 18 = 20/3
x^3 / xy = x^2 / y
20x^2 / 3y
Since Max's deck of cards contains the same number of blue cards as Barry's,
letting x as the number of red cards in Max's deck of card
40 / x = 8 / 9
Solving for x
360 = 8x
x = 45
There are a total of 40 + 45 = 85 cards in Barry's deck of cards
