One way:

=Base number / (1 + 0.07)

In article ,
John wrote:

I have a total of funds available of $3000 and tax of 7% and want to find out
what is the highest base price that I could enter and max out at $3000.
Base number + (Base number X .07) = $3000
I used the trial and error method and came up with $2804. What formula
could I use that would do this for me?