So the person makes $50,000 minus the base salary of $25,000 which means he must make $25,000 in commissions.
So we have to figure out $25,000 is 5% of how much. There are many ways to do this.
5% is like saying 5/100. So $25,000 x 100/5 = $500,000
Or, to go from 5% to 100% you multiply by 20. Therefore your answer is $25,000 x 20= $500,000