Answer:
A
Step-by-step explanation:
Triangle ADC and Triangle BDA are similar. So, we can setup ratios to solve for x.
Similar triangles has corresponding lengths proportional.
From Triangle ADC, CD corresponds to DA, so
From Triangle BDA, AD corresponds to DB.
Now we can write ratios as:
[tex]\frac{CD}{DA}=\frac{AD}{DB}\\\frac{15}{x}=\frac{x}{4}\\x*x=15*4\\x^2=60\\x=\sqrt{60} \\x=7.75[/tex]
rounding to nearest tenth, 7.7
correct answer is A
