Question 992778
Let us use the cosine rule first.

a = 50
b = 60
C = 30 degrees


{{{c^2 = a^2 + b^2 - 2abcos(C)}}}
{{{c^2 = 50^2 + 60^2 - 2*50*60*cos(30) = 903.8476}}}
{{{c = 30.06}}}


So largest side is b = 60 m.


Using Sine rule
{{{c/sin(C) = b/sin(B)}}}
{{{sin(B) = (b*sin(C))/c}}}
{{{sin(B) = (60*sin(30))/30.06}}}
B = 86.3 degree