tan(½x-20º)=1

If you just want the answer for    \(\tan(\frac12x-20º)\)  in the first quadrant...

\(\tan(\frac12x-20º)=1\\~\\ \frac12x-20º=\arctan(1) \\~\\ \frac12x-20º=45º \\~\\ \frac12x=45º+20º \\~\\ \frac12x=65º \\~\\ x=65º*2\\~\\x=130º\)

If you want the general solution please say so