1. **Stating the problem:** We are given the equation $a + b = ax$ and asked to express $a$ in terms of $b$ and $x$. 2. **Rewrite the equation:** The equation is $a + b = ax$. 3. **Isolate terms involving $a$:** Move all terms with $a$ to one side: $$a - ax = -b$$ 4. **Factor out $a$:** $$a(1 - x) = -b$$ 5. **Solve for $a$:** $$a = \frac{-b}{1 - x}$$ 6. **Explanation:** We factored $a$ from the left side and then divided both sides by $(1 - x)$ to isolate $a$. This gives the value of $a$ in terms of $b$ and $x$. **Final answer:** $$a = \frac{-b}{1 - x}$$