Hi,
The math doesn't seem right.
$300-50%=$150 is ok
$600-30%=$180 is not ok. Should be 420?

If $300 is in A2, then in B2: =A2-(A2*50/100)
If $^00 is in A3, then in B3: =A3-(A3*30/100)

If you really want 50% of 300 and 30% of 600:
in B2: =A2*50%
in B3: =A3*30%

Regards - Dave.