The best way to solve this is to make both denominators to be same number.
we need to multiply first numbers denominator with 3 and than both denominators will be 18
same we have to do with numerator of first number (multiply it by 3) and we get 15.
now we just compare. since 15 > 13 first number is greater.
Basically you need to expand one number in such way that they have same denominators (sometimes you will have to expand both for example if denominator are 3 and 7) and than just compare numerators...