Question 993971
x fish initially

YOUR DESCRIPTION IS WRONG!
{{{(1-2/3-2/5)*x=30}}}, and LCD is {{{3*5}}}.

{{{(15/15-(2/3)(5/5)-(2/5)(3/3))x=30}}}


{{{(15/15-10/15-6/15)x=30}}}


{{{((15-16)/15)x=30}}}


{{{(-1/15)x=30}}}


{{{x=30(-15)}}}


{{{x=-45}}} which makes no sense.  Recheck your problem description carefully.