Kindly verify the workings eh, thanks.

First part of the question needs the understanding that similar figures have proportional ratios, and these ratios are dimension specific: length ratios are one dimension, while area ratios are two dimension, and volume or mass are three dimension

Second part of the question is slightly tougher, in that it requires you to understand that similar triangles have that same length ratio, which can be applied for trigonometry as well.
For similar triangles ABX and CDX,
1) AB/BX = CD/DX : this is an example of similarity in that sides are relative to each other, and similar sides are related to one another in this manner.
2) AB/CD = BX/DX : this is an example of finding the proportionality constant between the two triangles; which is the length ratio at all three sides - BUT the two corresponding sides must be accurately defined i.e. AB is similar to CD, BX is similar to DX - essentially in this case, the larger triangle is 1.5 times as long as the smaller.