To know about independent and dependent variable, first we have to know about variables.
In mathematics, a variable is an event, idea, period or a type of category which we trying to measure. So we can say that a variable is anything that can be changed, like time,height,weight, attention etc.
In mathematics, we have two types of variables, independent variable and dependent variable. These two variables are the mathematical tools, used in an experiment. By the use of these tools, we control over the experiment and measure the result. These variables are related to one another.

In Math, independent variables are those values that determine the value of other variables.

A variable, which manipulated or controlled by human being or the experimenter is known as independent variable. It stands alone and isn't changed by the other variable(which we are trying to calculate). This is also called " factors".

This type of variable manipulated by the experimenter in an experiment. So we can say that,
independent variables are variables that are systematically controlled by any researcher to determine the variable’s overall effect on the final outcome or the dependent variable.

For example, someone's weight might be an independent variable. Other factors (such as what they eat, how much they eat, how is the food) aren't going to change a person's weight. In fact, when we are looking for some kind of relationship between variables we are trying to see if the independent variable causes some kind of change in the other variables, or dependent variable.

There are three ways to manipulate independent variables: presence or absence technique, amount technique and type technique.

In presence or absence technique, the independent variable can be manipulated by presenting a condition or treatment to one group of individuals and withholding the condition or treatment from another group of individuals.

In amount technique, the independent variable can be manipulated by varying the amount of a condition or variable such as the amount of a drug which is given to children within a learning disorder.

In type technique, the independent variable is to vary the type of the condition or treatment administered.