To make a negative number positive in math, you can use the absolute value function. The absolute value of a number is its distance from zero on a number line and it always returns a positive number regardless of whether the input was originally positive or negative. To calculate the absolute value of any given number, simply drop any negative sign before it and then proceed with your calculation as normal. For example, |-5| = 5; -5 becomes +5 when using the absolute value function.