As value of x = - 1 and y = 3 should be solution of a linear equations.
So such equation can be : x + y - 2 = 0
or 3x + y = 0
As x = - 1 and y = 3 are coordinates of a point in a plane and we know that we can draw infinite lines through a point in a plane so there are infinitely many equations are possible whose solution is satisfied by x = - 1 and y = 3