Let x be the degree of angle a.
Angle b: 20+3x
Angle c: 55+x
We know that all angles add up to 180 degrees.
180=x+(20+3x)+(55+x)
180= 5x+75
180-75=5x
105/5=x
21=x
Angle a: 21 degrees
Angle b: 20+3(21) => 83 degrees
Angle c: 21+55 => 76 degrees
Hope I helped :)
Because it doesn’t equal exactly 1.7 it equals about 1.73205
3/5 or 0.6 should be your answer