1. **State the problem:** Solve the equation $X + m - t = 150$ for $X$. 2. **Formula and rules:** To isolate $X$, we need to move the terms $m$ and $-t$ to the other side of the equation by performing inverse operations. 3. **Isolate $X$:** $$X = 150 - m + t$$ 4. **Explanation:** We subtracted $m$ and added $t$ to both sides to keep the equation balanced, isolating $X$ on one side. 5. **Final answer:** $$X = 150 - m + t$$