1. **State the problem:** We need to find the value of $B$ in the equation $15 + B = 23$. 2. **Use the formula:** To isolate $B$, subtract 15 from both sides of the equation. 3. **Perform the subtraction:** $$15 + B = 23$$ $$\cancel{15} + B = 23 - \cancel{15}$$ $$B = 8$$ 4. **Interpretation:** The value of $B$ that satisfies the equation is 8. 5. **Final answer:** $$B = 8$$