Question

what do you understand by equation?

Answer 1

A mathematical statement used to evaluate a value. An equation can use any combination of mathematical operations, including addition, subtraction, division, or multiplication. An equation can be already established due to the properties of numbers (2 + 2 = 4), or can be filled solely with variables which can be replaced with numerical values to get a resulting value. For example, the equation to calculate return on sales is: Net income ÷ Sales revenue = Return on Sales. When the values for net income and sales revenue are plugged into the equation, you are able to calculate the value of return on sales.

Read more: http://www.businessdictionary.com/definition/equation.html

Answer 2

In Maths, an equation is a mathematical statement. It has an "=" (read as "equal to") sign in between, and two equivalent expressions on its both sides. Let me give you an example.
5 + 2 = 7
This is an equation. This is a statement which consists of = sign in between and two equivalent expressions "5 + 2" and "7" on its both sides.
Another example…
5x + 5 = 2x + 2
This statement shows that the expressions "5x + 5" and "2x + 2" are equal.

Hope this may help you.