How can you tell if an equation is linear or non linear?

In a linear equation, the most power of x is 1

E.g. x+3, x-7

In a non linear eq, the power of x in more than 1 it can't be 1

step-by-step explanation:

10.50 + taxes which added up to 11.50

+25 = x

step-by-step explanation:

here x is the hypotenuse of a right triangle whose legs are 7 and 24.   by the pythagorean theorem, 7² + 24² must equal x²:

x² = 49 + 576 = 625.   thus, x = +√625 = +25 = x