Answer:
Given the two triangles are shown:
First triangle has sides x cm , 6 cm and 12 cm.
and
Second triangle has sides 20 cm , 8 cm and 16 cm.
Since, the given two triangles are Similar.
⇒there corresponding sides are in proportion.
i,e

(a)

Solve for x;
By cross multiply we have;

Divide both sides by 16 we get;
cm
(b)
Find x using the ratio sides:

By cross multiply we have;

Divide both sides by 8 we get;
or
cm
The value of x =15 cm in both a and b is same because the given two triangles are similar,
by definition of similarity, the given triangles have their corresponding sides are in proportion.