well, we don't know how many years we're talking about?
Let's say we want to know the prize after one year: it's 540 +540 18%.
another way of writing it is 540 118%. (this is 637.2)
after two years it will be:
540118%118%
we can also write it without =%: (as 100 % is always 1, 101% is 1.01 etc)
5401.1181.118
we can also make a more general statement:
n=number of years that have passed:
prize of the clock now=540*\(1.18^{n}\)
