What is the percent of 15 yards to 18 yards

3 goes into 18 six times.

What you have there is 5/6 as 3 goes into 15 five times.

5/6=0.83333 ...

So what you could say is that 15 yards is roughly 83% of 18 yards.

Likewise you could just get your calculator out and figure out what 15/18 is as a decimal ...

Turns out that it's 0.83333 ... as a decimal.

Once again, you've figured out that 15 yards is roughly 83% of 18 yards.