if the difference of a number and four is doubled the result is 1/4 less than the number. Find the number
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 $\displaystyle x-4$, 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 -> $\displaystyle 2(x-4)=x-\frac{1}{4}$ -> $\displaystyle 2x-8=x-\frac{1}{4}$ -> now you continue solving this equation for x and you will get the number.