Respuesta :
[tex]\text {Hello! Let's Solve this Equation!}[/tex]
[tex]\text {The First Step is to Add 21:}[/tex]
[tex]\text {9x-21+21=90+21}\\\text {9x=111}[/tex]
[tex]\text {The Final Step is to Divide 9:}[/tex]
[tex]\text {9x/9=111/9}[/tex]
[tex]\text {Your Answer would be:}[/tex]
[tex]\fbox {x=37/3}[/tex]
[tex]\text {Best of Luck!}[/tex]