How do u know if an equation is linear?

An equation is linear if its graph forms a straight line. This will happen when the highest power of x is "1". Graphically, if the equation gives you a straight line then it is a linear equation. Else if it gives you a circle, or parabola or any other conic for that matter it is a quadratic or nonlinear equation.

Step-by-step explanation:

it will cost dollar $540

the living room is 3 which means if we divide 325/3 then we get $108

therefore if 1part of the living room cost $108 and 3 costed $325

then total 5part of the room will cost 5*108 which gives $540