Answer:
The value of x is: 2.5 units
Explanation:
Two triangles are said to be similar if the ratio of the corresponding sides of the two triangles are equal.
i.e. if two triangles ΔABC and ΔDEF are similar such that the sides of the triangle ABC are a, b and c and the corresponding sides in ΔDEF are d,e and f respectively then we have:

Here we have the base length of the orange i.e. the quadrant above the x-axis as: 8 units
and the base length of the similar triangle i.e. triangle below x-axis as: 4 units.
i.e. we have: a=8 and d=4
and b=5 and e=x
Hence, we have:

i.e.

Hence, we have:
