Here is the equation:
[tex] 2x+11=21 [/tex]
Leave the variable alone by subtracting 2 from both sides:
[tex] 2x+11 = 21 \\ 2x - 11 = 21-11 [/tex]
The new equation becomes:
[tex] 2x=10 [/tex]
Leave the variable alone(again) by dividing both sides by 2:
[tex] 2x \div 2 = 10 \div 2 [/tex]
Simplify and it becomes:
[tex] x = 5 [/tex]