You can see that you have one variable, the number, let x be the unknown number, you can write difference of the number and 4 by , now the problem says that IF difference of the number and 4 is doubled, the result is 1/4 less then the number, so first thing that you should do is to double difference of the number and 4 and make it equal to 1/4 less then the number, you will get an equation -> -> -> now you continue solving this equation for x and you will get the number.