Given expression:
A =

Solve for b₁;
Solution:
This is a subject of the formula problem.
Given expression:
A =

First, multiply both sides by 2;
2 x A = 2 x
2A = b₁ + b₂
Then subtract b₂ from both sides;
2A - b₂ = b₁ + b₂ - b₂
b₁ = 2A - b₂
The solution is b₁ = 2A - b₂