What is an equation?

What do you notice about each of the following?
11 + 3 = 15
25 - 5 = 20
The right hand side is equal to left hand side.
An equation is a statement that two expressions are equal. For example, the expression 12+3 is equal to the expression 16-1(because they both equal 15), so we can write the following equation:
12+3=16-1

When the left-hand side was equal to the expression on the right-hand side then the equation is called true equations. Let's make sure we understand what a true equation is.
8+2 = 5+5
7-3= 4+1
Here one thing must be clear to you that 5+3 is an expression and it is numerical expression but if the expression includes variable then it is algebraic equation. For example, the equation x+2=6 has a variable in it.

How can we solve algebraic equation?

3 + Z =  17

if Z=14, then 3 + 14 = 17.