cyclic quadrilateral
This statement is always true:
Opposite angles add up to 180°
Answer:

Step-by-step explanation:

If point Y is between points X and Z, then
XY + YZ = XZ
In words, the distance from X to Y, plus the distance from Y to Z, is equal to the distance from X to Z. (See the attached picture.)
So 6b + 8b = 175
Can you finish it?
Here's number 5. If you need more explanation just let me know.
24, just do 6x4 because there are 4 sides.