A current of 0.99 A flows in a wire. How many electrons are flowing past any point in the wire per second

The charge on one electron is 1.60e-19

0.99A is the same as 0.99 coulombs per second (0.99C/s).
1 electron carries 1.6E-19 coulombs
You just divide: 0.99 / 1.6E-19 = 6.2 x 10E18 electrons per second.

Notes.
'10 to the power -19' can be written as 10E-19, but don't use a small 'e' as this is something different.

To understand the problem, imagine the current was 50A i.e. 50 coulombs per second, and each electron was 2 coulombs. It's easy to see there must be 50/2 = 25electrons per second. The problem is solved the same way but with different numbers.

current I=Q/t ______1

and Q = ne _______2 n=no of electrons,e=charge on electron

combining eqn 1 and 2

I= ne/t

so, no of electrons per second n/t= I/e

=> n/t=0.99/1.60*10^-19

=> 6.18 *10^18 electrons/sec
your answer thank you..

2 electrons