Hello thereddevilsThis is copied from here, because I think you got the questions mixed up.
Assuming that the quote here refers to the question in this post, note that you need to use similar triangles, not congruent ones. The two triangles and are similar, because their angles are all equal. And the key fact is that corresponding sides - those opposite to equal angles - are in the same ratio. Since we've marked the angles in red, blue and yellow, it's very easy to see which are pairs of corresponding sides. We write their ratio as a set of fractions, like this:
Plug in the numbers you've been given, and solve for the side you want.
Grandad
Hello, thereddevils!
LPM is a straight line and .
Name the angle equal toCode:N * ** * * * * * * * * * * . * * * L * * * * * * * * * * * M P
Make two diagrams . . .
LetCode:N * ** * * * * * * * * * * * 2 1 * * * * * * P
is the third angle of the triangle.
Code:N * * 1 * * * * * * * * 2 * L * * * * * * * * * * * M P
We have: .
is the third angle of the triangle.
Therefore: .
Edit: Too slow again . . . Too fast for me, Grandad!
.