$\frac{5}{15}=$

Step 1 ：Find the greatest common divisor (GCD) of the numerator and the denominator: GCD(5, 15) = 5

Step 2 ：Divide both the numerator and the denominator by the GCD: \(\frac{5}{5}\) = 1, \(\frac{15}{5}\) = 3

Step 3 ：Write the simplified fraction: \(\boxed{\frac{1}{3}}\)