First, look at the variables represented by letters. Is there a letter common to the three terms? Yes: q is common so put q to one side as a factor. Take q out of the three terms: 330pr-5p+50.
There are no more letters common to all three terms, so look at the numbers and look for a common factor.
5 goes into each of the three numbers so we can put 5 with q as a common factor 5q. If we divide all the terms by 5 we get: 66pr-p+10, so we have 5q and 66pr-p+10 as the main factors, and we write this as:
5q(66pr-p+10). That's the final answer, unless we want to factorise within the parentheses. We can group the first two terms: 66pr-p is p(66r-1), isolating p as the common factor. We get 5q(p(66r-1)+10).