Question

Math help pls!! answer choices are 17.1 , 3.5 , 8.4 , and 1.5

Answer 1

Triangles ABD and BCD are similar, because they are both right and share a common angle, and thus all three angles are equal.

This means that we can set the proportion

$AB\div AD = BC\div DC$

Plug the numbers and we have

$5\div 3.5 = 12\div x$

Solve for $x$:

$x=\dfrac{12\cdot 3.5}{5}=8.4$