Grandma took 500 yuan to go shopping with Fangfang, a set of sportswear was 245 yuan, and a pair of sports shoes was 155 yuan. How much should grandma get back when she buys these two commodities?
奶奶带了500元和芳芳逛商场，一套运动服245元，一双运动鞋155元．奶奶买这两样商品，应找回多少钱？
<gadget id="calculator">245 + 155</gadget>
<output>400</output>

<gadget id="calculator">500 - 400</gadget>
<output>100</output>

<result>100</result>