### Theory:

"Life is a linear equation in which you can't cross multiply! If you think you can do it, you can do it. If you think you can't do it, you can't do it. It's a simple formula."

~Israelmore Ayivor.

In your previous class, you have studied the linear equation with one variable and using these equations you can solve the mathematics problems and our real-life problems as well.

But at some circumstances, we ought to use more than one variable in an equation.

Let's see an example to understand it.

In a One-day International Cricket match between India and Australia two Indian batsman scored 153 runs together.

In this above scenario, we can observe that the score of neither of them is known. So, there are two unknown quantities. Let us take that as $$x$$ and $$y$$ respectively.

Therefore, $$x + y$$ $$=$$ 153. This is the required linear equation two variables. To represent the two variables, we can use the other alphabets as well.
Example:
1. $$a + b$$ $$= 100$$

2. $$20s +10t$$ $$= 225$$

3. $$0.2p +20.5q$$ $$= 332.5$$

4. $9=\sqrt{10b}-40c$