Bertha plays tennis. Every ten games, one of her tennis balls wears out. Every five games, she loses a ball. Every four games, she buys a canister of three balls. She started with two balls and gave one to her partner. After twenty games, how many tennis balls does she have?
Bertha wears out 20 / 10 = 
<gadget id="calculator">20/10</gadget>
<output>2</output>
2 tennis balls in 20 games.
She loses 20 / 5 = 
<gadget id="calculator">20/5</gadget>
<output>4</output>
4 tennis balls in 20 games.
She buys canisters of 3 * 20 / 4 = 
<gadget id="calculator">3*20/4</gadget>
<output>15</output>
15 tennis balls in 20 games.
Bertha started with 2 balls and gave 1 away, so she has 2 + 15 - 2 - 4 - 1 = 
<gadget id="calculator">2+15-2-4-1</gadget>
<output>10</output>
10 tennis balls after twenty games.

<result>10</result>