Question

What is the value of y?

Answer 1

Apply the Pythagorean Theorem on the triangle NTM:
$(NT)^2+(TM)^2=(NM)^2 \\~\\~\\y^2+6^2=(9+3)^2 \\~\\~\\y^2+36=144\\~\\~\\y^2=108\\~\\~\\y=6 \sqrt{3}=~10.39$

I hope that helps!