The expression is 13 of 27.
The percent is 0.13 and the whole is 27. You need to find the part.
\Let n represent the part.
\Part = percentwhole
n = 0.1327 (Substitute percent = 0.13 and whole = 27)
n = 3.51 (Multiply: )
3.51 is 13 of 27.