The answer is 60. Let x be the number we are looking for. So x is 100% and we know that 15 is 25%. Make a proportion: x : 100% = 15 : 25%. Cross the products: x * 25% = 15 * 100%. x * 25% = 1500%. x = 1500% : 25%. x = 60. Thus, 60 is 100%, and 15 is 25% of 60.