Simplify the like terms in an equation involves combining the elements that belong to the same group. In other words: in all first-degree equations with one unknown, there are elements that belong to the group of unknowns (variables) and elements that belong to the group of numbers. The goal is to unite all the elements of each of the mentioned groups into respective sides to thus arrive at the result of the equation.

**For example**

$X+2X=5+1$

In this equation, we can clearly see that the elements $X$ and $2X$ belong to the group of unknowns, and therefore, we can combine them.

Conversely, the elements $5$ and $1$ belong to the group of numbers and thus can also be combined.

$3X=6$

$X=2$

The result of the equation is $2$.