m + n = 110o, (n + r) = 130o
(m + n) = 120o
then, r = 130o - n
and;
m + (130^o - n) = 120o
m - n = -10o
2m + (n + r) = 110 + 120 = 230
2m + 130 = 230
2m = 230 - 130
m = 1002 = 50o
n = 110o - 50o
= 60o
r = 130o - 60o = 70o
Hence, the ratio m : n : r
= 50 : 60 : 70
= 5 : 6 : 7
