How many buttons did you buy in total if you sewed 5 buttons on each outfit and 3 buttons remained after 15 sets were nailed?
给服装钉扣子，每套服装钉5颗，钉完15套后还剩3颗，一共买了多少颗扣子？
<gadget id="calculator">5 * 15</gadget>
<output>75</output>

<gadget id="calculator">75 + 3</gadget>
<output>78</output>

<result>78</result>