The arc measure, which corresponds to the central angle measure, is always twice the subtended angle.
So 60 is twice a,
Answer: a=30
84 is twice b
Answer: b=42
60 + 100 is twice c,
Answer: c=80
d is what's left of the circle, total 360 degrees,
d = 360 - 84 - 60 - 100 = 116
Answer: d=116