Answer:
8
Step-by-step explanation:
Sum of length on bottom side: 3 + 1 = 4
Sum of lengths of top side: x
Larger length on bottom side: 3
Larger length on top side: 6
Since the two lines are cut by three parallel lines, the segment cut off are of proportional lengths.
4/x = 3/6
4/x = 1/2
x = 8
