You must use Pythagorean theorem, which is
![a^(2) +b^(2) =c^(2)](https://img.qammunity.org/2020/formulas/mathematics/college/ysyqcuv7zowodz5o2fvprirk5nq313c0wc.png)
a and b are both legs (the two legs are the sides that form a perpendicular right angle) while c is the hypotenuse (side opposite the right angle)
In this case...
a = y
b = 8
c = 12
^^^Plug these numbers into Pythagorean theorem
![y^(2) +8^(2) =12^(2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/5mfrdr1rchue6xofd62nuwiuec1zuv3sk7.png)
Simplify as much as possible
+ 64 = 144
Isolate y by subtracting 64 to both sides
+ (64 - 64) = 144 - 64
= 80
Further isolate y by taking the square root of both sides. This will take away the square from the left side
y =
![√(80)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/gp06lj2knip1nutmoj9x7gvepw5nzvcd59.png)
<<< Can be further simplified
4√5 = y
Hope this helped!
~Just a girl in love with Shawn Mendes