So to find the midpoint in this, you have to find the average of your 2 points (-21 and 18)! So the average of -21 and 18 is -1.5! So that means your midpoint (or in this case your x,) is -1.5!
⭐ Please consider brainliest! ⭐
✉️ If any further questions, inbox me! ✉️