I have a few homework questions that I just don't understand. It would be greatly appreciated if you show me step by step how you got them, thank you very much!!

1) Solve for H--- S= 2(hw+hl+wl)

2) Solve for P---- A=P+ Prt

3) Solve the equation (4/4x+9)+ (7/4x-9)= 44x+27/16x^2-81

4) Solve the equation (2/5x+4)-(4/10x+8)