you have to rearrange it since you need the (I) to get the charge flow.
So the formula is P =I2r
If you put it in a triangle it would be
P
I2 x R
And since you want the "I" you cover it and that would mean I = P x R. However, the I has a squared in front of it, so you must do the opposite and square root it. So it would be Square root P/R
Hope that helps Anymore questions feel free to let me know