Without factoring in the cost of depreciation for his car John made $30,000 doing Uber.  When he finally traded in the car he bought for $18,000 he got $6000 back.  What was his profit from driving Uber?
His car depreciated 18000-6000=$
<gadget id="calculator">18000-6000</gadget>
<output>12_000</output>
12000.
So he made a profit of 30000-12000=$
<gadget id="calculator">30000-12000</gadget>
<output>18_000</output>
18000.

<result>18_000</result>