I just need the equation on how to do it. I'm so lost :'( help please!!!!!!

The '120-V' is what we in the engineering profession call a "red herring".You don't need it to solve the problem.  The answer would be the sameif the blow drier were operating from a 440-V outlet, or any other kind(just as long as the blow drier is designed to operate on whatever voltageit was plugged into.)Power = 750-W = 0.75 kWTime = 13 minutes = 13/60 of an hourEnergy = (power) x (time) = (0.75 kW) x (13/60 of an hour) = 0.1625 kWhCost per unit of energy = $ 0.1 per kWhTotal cost = (energy) x (cost per unit of energy)Total cost = (0.1625 kWh) x ($ 0.1 per kWh) = $ 0.01625 = 1.625 cents===============================The other answer has his significant figures correct, but shows what happens when you don't carry your units all the way through.

[tex]750W=0.75 kW\\ \\ 0.75*\frac{13}{60}=0.1625 \ kWh\\ \\ \boxed{0.1625*0.10=\$ \ 0.1625}[/tex]