1. **State the problem:** We have a quadrilateral with four angles: 70°, 76°, 90°, and an unknown angle $r$. We need to find the value of $r$. 2. **Recall the formula:** The sum of the interior angles of any quadrilateral is always 360°. This is given by: $$70^\circ + 76^\circ + 90^\circ + r = 360^\circ$$ 3. **Add the known angles:** $$70 + 76 + 90 = 236$$ 4. **Set up the equation to solve for $r$:** $$236 + r = 360$$ 5. **Isolate $r$ by subtracting 236 from both sides:** $$r = 360 - 236$$ 6. **Calculate the value:** $$r = 124$$ **Final answer:** $$r = 124^\circ$$