Solving for roots. I need to explain the procedure to my twelve year old bro who's failing his math class, unfortunately I haven't been able to be of much help, so I'm hoping that you guys can. plus the kind of roots the last three equations have. Thanks

a) 6(80-30) = 48-x

b) 2x^2-13x+6 = 0; by factoring

c) 3x^2 - 24x + 48 = 0

d) 4x^2 + 7 = 0

e) 4 (7x-4)^2 +1 = 9