You now have had practice solving equations with one variable and equations with two variables?

Hello!

An one variable equation is a line in a two-dimensional "space". For example 2x-5=3 => x=4 represents a line parallel to x-axis that start from the number 4. In fact it represent a constant number.

Now, if u have a two variable equation like a)y-2x=5 => y=2x+5 it represents the linear equation in two-dimensional space.
b) x^2+y^2=9 is a two variable equation too, but now represents a cirle.
c) x^2-y=0=> y=x^2 represents the quadratic equation in two-dimensional space.
d)y^3-x=5 represents a cubic equation etc....

But if u have a 3 variable equation, like x+y=z=2 or x^2-2y+z=1, it represents a curve in a 3-dimensional space.

To conclude:
A)1-variable= representation of a number (2D)
B)2-variables= curves in two dimensions (2D)
C)3-variables= curves in three dimensions (3D)

In Physics many times, are used 4 variable equations. So u have x,y,z as space variables and t as the time variable. A 4-dimensional equation cannot be drawn, it's a dynamical system that always changing (moving) Unlikely we are beings that living in a 4D Time-space and we cannot deeply understand(imagine) what a higher variable equation represents.