Question 1107069
The midpoint of xy is z, if xy=3n and xz=n+15, what is yz? 
:
x------z------y
|-----3n------|
|-n+15-|
:
{{{(3n)/2}}} = n + 15
3n = 2(n+15)
3n = 2n + 30
3n - 2n = 30
n = 30
therefore
xy = 30 + 15
xy = 45
xy = yz, therefore
yz = 45