Chapter 9 - Section 9.1 - Solving Systems of Linear Equations in Three Variables and Problem Solving - Exercise Set - Page 639: 36

20 degrees, 50 degrees, 110 degrees

long angle = 90 + small angle middle angle = 30 + small angle $l = 90+s$ $m = 30+s$ $l+s+m = 180$ $90+s + s + 30+s = 180$ $120 + 3s=180$ $3s= 60$ $3s/3 = 60/3$ $s= 20$ $l=90+s$ $l = 90 +20$ $l=110$ $m = 30+s$ $m=30+20$ $m=50$