Answer:
7.25
Explanation:
I gave you the answer earlier too!
for more info !
there s a theorem called MIDPOINT THEOREM
Which means the 3rd side of the triangle is equal to 1/2 of the line drawn by joining the mid points
so AB=1/2of YZ
which means
2x-4 = 1/2×21
thus, 2(2x-4) =21
=> 4x-8 = 21
4x = 29
x= 29/4 = 7.25