Please help if you can !

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

How to find the exponential function y=ca^x, with points (1,2) and (2,1)

Answer asap! show all work! find the number of complex roots, the possible number of real roots and the possible rational roots of the polynomial function. then, solve for all roots. x^3 + 2x^2 + 3x + 6 = 0