**Hint:** In this question remember to use the given information to form an equation and also remember $\dfrac{3}{7} - x = \dfrac{5}{4}$ where x is the required number, the given information will help you to approach the solution of the problem.

**Complete step by step answer:**

According to the given information, we know that subtracting a number from $\dfrac{3}{7}$ we get $\dfrac{5}{4}$

So, let x be the number when it gets subtracted from $\dfrac{3}{7}$ we get $\dfrac{5}{4}$

Therefore, $\dfrac{3}{7} - x = \dfrac{5}{4}$

$ \Rightarrow $$x = \dfrac{3}{7} - \dfrac{5}{4}$

$ \Rightarrow $$x = \dfrac{{12 - 35}}{{28}}$

$ \Rightarrow $$x = \dfrac{{ - 23}}{{28}}$

**Therefore, $\dfrac{{ - 23}}{{28}}$ is the number we required.**

**Note:** In the above question was based on the concept of linear equation in one variable which can be explained as the equation which contains one variable the general representation of linear equation in two variable is given as ax + c = 0 here a and c are the integers and x is the one variable in the equation which means that its value is unknown, these equations have only one solution there are more types of equations such as the linear equation of two variables which have only one dissimilarity than linear equation in one variable that are linear equations with two variables consist of two variable and it consists of two solutions.