Question

Please help need to finish ASAP

Answer 1

Look at the picture.

The triangle ADC and the triangle CDB are similar.

Therefore corresponding sides are all in the same proportion:

$\dfrac{y}{4}=\dfrac{12}{y}\ \ \ \ |cross\ multiply\\\\y^2=48\to y=\sqrt{48}\\\\y=\sqrt{16\cdot3}\\\\y=\sqrt{16}\cdot\sqrt3\\\\y=4\sqrt3$

Answer: 4√3