Solve For R 38D651

1. **State the problem:** Solve for $r$ in terms of $s$, $t$, and $u$ given the equation: $$s = t + u + r$$ 2. **Formula and rules:** To isolate $r$, we need to rearrange the equation by moving $t$ and $u$ to the other side using subtraction. 3. **Isolate $r$:** $$s = t + u + r$$ Subtract $t$ and $u$ from both sides: $$s - t - u = \cancel{t} + \cancel{u} + r - t - u$$ Simplifies to: $$r = s - t - u$$ 4. **Explanation:** We moved $t$ and $u$ to the left side by subtracting them from both sides, which leaves $r$ alone on the right side. 5. **Final answer:** $$\boxed{r = s - t - u}$$