Alright. Take x as Alan's age, and y as Bea's age. We can start writing equations; from the first sentence, we find that x - y = 3. From the second sentence, x + y = 27. Adding the two equations, gives 2x = 30. Thus, x is 15, and it follows, that y = 15 - 3, or 12. So for A, Alan is 15, and Bea is 12, and for B, Bea is 15, and Alan is 12.
If there is 6 percent sales tax, that means for every dollar the item you bought was ($18) there will be 6 cents added to it. So you would take 6 percent of or times 18 dollars which is 1.08. Then add those two together to get Final answer. The stereo is $19.08 dollars.
