Question

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

Answer 1

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 same
if 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 voltage
it was plugged into.)

Power = 750-W = 0.75 kW
Time = 13 minutes = 13/60 of an hour
Energy = (power) x (time) = (0.75 kW) x (13/60 of an hour) = 0.1625 kWh

Cost per unit of energy = $ 0.1 per kWh
Total 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.

Answer 2

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