Xiaohong buys 5 English books and 2 diaries, pays 7 yuan in total, and gets back 2.2 yuan. Knowing that each English book is 0.5 yuan, how much is each diary?
小红买5本英语本和2本日记本，共付7元，找回2.2元，已知英语每本0.5元，日记本每本多少元？
<gadget id="calculator">0.5 * 5</gadget>
<output>2.5</output>

<gadget id="calculator">7 - 2.2 - 2.5</gadget>
<output>2.3</output>

<gadget id="calculator">2.3 / 2</gadget>
<output>1.15</output>

<result>1.15</result>