An IF function has the syntax

=IF(test,Do_if_TRUE,Do_if_FALSE)

Your IF has a test [J12=40], a TRUE condition [J12], a FALSE condition [(X12/J12)*2080], at that point you need a closing parenthesis, you can't have any more (although you can nest further IFs in the TRUE or FALSE sections).

Can you explain in words what you want the formula to do?