29.99-20%= 23.99
25.00-10%= 22.50 so, Mr.chang got the better deal ( but not by much.)
I agree those answers make more sense to be true ^^^^

has characteristic equation

which has roots at

. The negative root has multiplicity 2. So the general solution is
Times the bottom equation by -4 to cancel out the x’s.
Add the equations.
Solve for y.
Plug in y to find x.