B is the cost of the game (some unknown amount). Subtract off 0.18B to indicate a 18% reduction in the price. That's how we get choice E.
Simplifying choice E leads us to choice A. Notice that 1 - 0.18 = 0.82; which represents 100% - 18% = 82%. After the discount, Bo is paying 82% of the original price.
Side note: Choice B indicates an 18% increase. Choices C and D don't represent percentage decreases (rather they're decreasing by a fixed amount regardless of what B is).
