7
1) Since this is an isosceles trapezoid, then 2 sides of that polygon have the same measure. Not the bases as we can see.
2) So we can state that side YZ and XW have the same length, so we can equate them:
YZ = XW Plugging into them the lengths
y+6 = 12 Subtract 6 from both sides
y = 12 -6
y =6
Considering that y= 6 units, then we can plug into XY length expressed by y+1.
XY
y +1 Plug y = 6
6 +1
7
3) Hence the length of XY is 7 units