find the measures of a,b,c

Lets Name The Upper Line m And Lower Line n.

And Let The Triangle Be BDE.

Its Clear That Line m Is Parallel To Line m

And DB And EB Acts As A Transversal.

D And 115 Are Forming A Linear Pair

So Angle D = 180-115 = 65

And Angle E = 180-120 = 60

Now By Angle Sum Property

B+D+E = 180

B+125 = 180

B = 55

So b = 55

115 And a Are Forming The Pair Of Co Interior Angles So Their Sum = 180

a = 180-115 = 65

c = 180-120 = 60

So Angles Are

b = 55,a = 65 and c = 60