You have the following equation:
y = -5x + 3
in order to determine if the point (0,3) is solution of the previous equation, replace the values of x = 0 and y = 3, and verify if the equation is consistent, as follow:
3 = -5(0) + 3
3 = 3
the equation is consistent for the given point, then, the point (0,3) is a olution of the given equation
