I assume here that the day here is the 24 period. This means that if the bacteria doubles every 2 hours, this will happen 12 times (24/2=12).
So Colby will have 50*2*2*2*2*2*2*2*2*2*2*2*2=50*4*4*4*4*4*4=200*4*4*4*4*4=800*4*4*4*4=3200*4*4*4=204800 bacteria.
if the bacteria doubles every 3 hours, this will happen 8 times (24/3=8).
So Jaquan will have
x*2*2*2*2*2*2*2*2=x*4*4*4*4=x*16*16=x* 256
So if we want so have the same amount:
204800=x*256
x=800
So he needs to start with 800.