Xiaohong buys a box of yogurt and a piece of bread every day. Each box of yogurt is 2 yuan and 10 cents, and each bread is 9 cents. How much does Xiaohong spend on yogurt and bread in a week?
小红每天要买一盒酸奶和一个面包，每盒酸奶2元1角，每个面包9角，小红一星期买酸奶和面包共要花多少元？
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">2 + (1/10)</gadget>
<output>21/10 = around 2.1</output>

<gadget id="calculator">(21/10) + 0.9</gadget>
<output>3</output>

<gadget id="calculator">3 * 7</gadget>
<output>21</output>

<result>21</result>