The current in an electric hair dryer is 12A. How many electrons flow through the hair dryer in 5.2 min ?

"Ampere" means 1 coulomb of charge every second.

12A means 12 coulombs of charge every second.

5.2 minutes = (5.2) x (60 seconds) = 312 seconds

12A for 312 seconds means (12) x (312)  = 3,744 coulombs of charge

1 coulomb is the amount of charge carried by 6.24 x 10¹⁸ electrons .

So 12A for 312 seconds means (3,744) x (6.24 x 10¹⁸) electrons.

That's  2.336 x 10²² electrons .

or  23,360,000,000,000,000,000,000 electrons .

(rounded to the nearest 10 quintillion).