An antique clock cost 540. its price is increased by 18% in a year

Assuming that you asking for the price of the clock after on year here's how to solve this:

The first step you need to do is find 18% of 540. Now these irregular numbers may seem intimidating to you, but just apply it to real life scenarios. If there are 10 questions on your test, and you get 9 correct, you get a 90%. 90% of 10 is 9. (Note, whenever you see "of" that usually means to multiply, and "is" means equal). A percent is just the percent number/100. 
With this knowledge, 18% =18/100 which can be simplified to 9/50.
Now multiply this by 540 as we multiplied 9/10 by 10. 
9/50 x 540 = 486/5 = 97 1/5 = 97.20
Now we add 97.20 (18% of 540) to 540
97.20 + 540 = 637.20

Final after one year the price of the antique clock is $637.20