Question

The point (0,3) lies on the graph of the linear equation 3x+4y=12

Answer 1

The statement is True.
3(0)+4(3)
=0+12 =12
So LHS=RHS

Hope it helps you.

Answer 2

Technically speaking if you want to verify whether the point lies on the graph of the given equation then just put the value of y coordinate in place of y and x coordinate In place of x.
If the value comes out to be 12 then the point is a solution of the given equation and hence lies on the graph of the given equation.