Wrong information – ASVAB Air Force Mastery Review

I've found math mistakes in both the answers and the explanations of this app. I definitely won't be paying $15 for the "full" version. Ex (4x^2+5y+6)-(6x^2+3y+8) reduces to -2x^2+2y-2 which wasn't even an option. 10x^2+2y-2=wrong
Review by User21223 on ASVAB Air Force Mastery.