QUICK HELP PLS!! Tell all steps :) 100 POINTS!!

The two triangles above are similar.

Find x using the ratio of the sides 12 cm and 16 cm:
x
20
=
12
16
. Show your work.

Find x using the ratio of the sides 6 cm and 8 cm. Show your work.

Explain why the answers to (a) and (b) should be the same.