The ratio between the angles of the quadrilateral is 3:4:5:6
that means smallest :3x , largest:6x.
consider a triangle with angle a , b ,c
a= smallest , b= largest, c= second largest
as per given info:
a= 2/3*(3x) = 2x
b= 2*a = 2*2x =4x
i.e c = 180-(a+b) = 180- 6x
we have to find second largest angle of the triangle and the largest angle of the quadrilateral:
== c (second largest angle of the triangle) + 6x( largest angle of the quadrilateral )
= (180 – 6x) + 6x= 180