First of all, we need to deduce the price of a single camera:
[tex]\dfrac{1800}{12}=150[/tex]
Now, we know that he profits 36 dollars from each camera. So, we are asking: which percentage of 150 is 36? We have
[tex]36 = 150\cdot\dfrac{x}{100}[/tex]
This equation literally says: 36 is x-percent of 150. And we need to solve for x:
[tex]x=\dfrac{36\cdot 100}{150} =24[/tex]
