It is known that the primary school holds art exhibitions for students of all grades, of which 18 are not in the sixth grade, and 20 are not in the fifth grade. Now that there are 22 paintings in the fifth and sixth grades, how many paintings in other grades are there in total?
已知小学举行各年级学生画展，其中18幅不是六年级的，20幅不是五年级的，现在知道五、六年级共展出22幅画，那么其它年级共展出多少幅画．
<gadget id="calculator">20 - 22</gadget>
<output>-2</output>

<gadget id="calculator">18 + (-2)</gadget>
<output>16</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<result>8</result>