Question

The triangles are similar by the AA Similarity Postulate. Find the value of x.

Answer 1

If the triangles are similar, then the sides are proportionate and the bases are as well.  Set up the proportion like this, with side lengths on top and base lengths on bottom: $\frac{4}{5}= \frac{12}{x}$.  Cross multiply to get 4x = 60.  That means that x = 20.

Answer 2

Answer:

A. 15

Step-by-step explanation:

We have been given that the triangles are similar by AA similarity postulate.

Since we know that corresponding sides of similar triangles are always proportional. Let us set proportions of corresponding sides equal to find the value of x.  

$\frac{4}{4+8} =\frac{5}{x}$    

$\frac{4}{12} =\frac{5}{x}$

Upon cross multiplying our equation we will get,

$4x =12\cdot 5$

$x=\frac{12\cdot 5}{4}$

$x=3\cdot 5$

$x=15$

Therefore, the value of x will be 15 and option A is the correct choice.