Hey there! :D
So, the angle measuring 100 degrees is supplementary to the angle that is adjacent to it, next to the one that is 60 degrees.
180-100= 80
It is 80 degrees.
80+60+x= 180
140+x= 180
Subtract 140 on both sides.
x=40
40 is the answer.
I hope this helps!
~kaikers
