Simplify to a fraction in lowest terms: \(\frac{\mathrm{6+9} }{\mathrm{6 \times 9}} \)

Perform the addition indicated in the numerator: \(6+9=15\)
Perform the multiplication indicated in the denominator: \(6 \times 9 = 54\)
Present as fraction: \(\frac{\mathrm{15} }{\mathrm{54}}\)
When simplifying a fraction, you divide both the numerator and the denominator by their greatest common divisor (GCD) to reduce the fraction to its lowest terms.
In this case, the GCD of 15 and 54 is 3.
Therefore, lowest terms of this case are : \(\frac{\mathrm{15} }{\mathrm{54}} \div \frac{\mathrm{3} }{\mathrm{3}}=\frac{\mathrm{5} }{\mathrm{18}}\)