*** I AM EDITING because I misread the question before ****
Angles N + E + D = 180 because all 3 inside (interior) angles of a triangle always add up to 180.
Angle E = D-10
Angle N = 16+D
Let's see what we can solve by substitution:
N + E + D = 180
Since N = 16+D
16+D + E + D = 180
2D + 16 + E = 180
2D + E = 164
E = D-10
2D + (D-10) = 164
3D = 164+10
3D = 174
D = 58
So N = 16+D
N = 16+58
N = 74
E = D-10
E = 58-10
E = 48 (aka angle NED)
Angle BEN = 180-(angle NED) = 180-48 = 132
So Angle BEN = 132