Find the value of x. please help me.

Acircle has a diameter will endpoints of (-2,8) and (6, 4). what is the center of the circle

Jenisey has $24 to spend on seven pencils. after buying them she had $10. how much did each pencil cost.?

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.