Answer:
Option -3 Equation 3 -
Explanation:
Given : Equation 1 -

Equation 2 -

Equation 3 -

Equation 4 -

To find : Which equation represents a linear function?
Solution :
A linear function - It is in the form
.
A linear function has one independent variable and one dependent variable.
A linear function is a polynomial of degree one or zero.
From the following equation only equation 3 is a linear function,because it has one independent variable -1 and one dependent variable y on x and a polynomial of degree 1.
Therefore, Equation 3 -
is a linear function.