Cramer's rule tells you that the value of x in the system of equations
is given by
In matrix terms, this is the determinant of the coefficient matrix with the right-side constants replacing the x-coefficients divided by the determinant of the matrix of coefficients. The value of y can be found by doing similar math with the numerator being the determinant of the coefficient matrix with the right-side constants replacing the y-coefficients. For systems of higher dimension, the column of right-side coefficients replaces each column of variable coefficients in turn.
For your equations, this evaluates to