Given
[tex]A=7B+C[/tex]Solution
Step 1
Subtract C from both sides
[tex]\begin{gathered} A-C=7B+C-C \\ A-C=7B \end{gathered}[/tex]Step 2
Divide both sides by 7
[tex]\begin{gathered} \frac{A-C}{7}=\frac{7B}{7} \\ \text{Simplify} \\ B=\frac{A-C}{7} \end{gathered}[/tex]The final answer
[tex]B=\frac{A-C}{7}[/tex]