Li Hong and Wang Gang bought 5 and 3 copies of the same exercise book. It is known that Li Hong paid 7.20 yuan more than Wang Gang. What is the unit price of this exercise book?
李红和王刚买同一种练习本5本和3本，已知李红比王刚多付7.20元，这种练习本的单价是多少元？
<gadget id="calculator">5 - 3</gadget>
<output>2</output>

<gadget id="calculator">7.2 / 2</gadget>
<output>3.6</output>

<result>3.6</result>