can i not do XY = 26 - 21? since it is an overlapping part?

I solved by trying the questionâ€™s answers. We have to choose a number which satisfy the relation of YZ it twice WX.

A) WX=21 - 5 = 16 , YZ = 26-5=21 (Wrong, YZ it not twice WX)

B) WX=21 - 10 = 11 , YZ = 26-10=16 (Wrong, YZ it not twice WX)

C) WX=21 - 11 = 10 , YZ = 26-11=15 (Wrong, YZ it not twice WX)

D) WX=21 - 16 = 5 , YZ = 26-16=10 (Correct, YZ it twice WX)

yes but can i not do XY = 26 - 21? since it is an overlapping part? that is XY = XZ - WY?

No, you cannot. The overlapping part XY is included in the two segments so you can subtract the two other segments to find the answer but it does not equal the common part. Kindly find below explanation:

Given:

WY = WX+XY = 21

XZ= XY+YZ = 26

Find:

XZ - WY = XY + YZ - WX - XY

= YZ-WX (which definitely cannot equal XY)

= 26 - 21 = 5