Given the equation :
[tex]a+4=11[/tex]To find a add (-4) to both sides
[tex]\begin{gathered} a+4-4=11-4 \\ \\ a=7 \end{gathered}[/tex]check the answer by substitution with a in the left hand side
so,
[tex]\text{LHS}=7+4=11=\text{RHS}[/tex]So, the answer is : a = 7