Question

Find the value of a.
A. 3
B. 5
C. 8
D. 11

Answer 1

@Kainui

Answer 2

I assume b like the next figure here.


I think about two figures.


Figure 1 and figure 2 are similar figures.
So,
\[b : 18+(a+5) = 18:b\]
\[18\times(18+a+5) = b \times b\]
Here,　I use Pythagorean theorem.
\[18^{2} + 12^{2} = b^{2}\]

Therefore this question is
\[18 \times (23+a) = b^{2} = 18^{2} + 12^{2}\]
\[18 \times (23+a) = 468\]
\[23+a=26\]
a=3
The answer is "A".