How do I multiply a percentage

Hello,

I am trying to create a formula in Numbers and continue to get a syntax Error. So frustrating. Can anyone help

I have two cells...

B39 with $2800 in it.

I have tried

=B39x20%

=B39x.2

=(B39)x(.2)

and so on and so forth and I keep coming up with a syntax Error. Excel does this with no problem.

Any help would be greatly appreciated.... All want to do is multiply a number

Thanks, Joe