geometry

15x+5+60+22x+4=180

37x+69 = 180

37x = 111

x=3

Angle ∠CDB is just 180 - 120 = 60 degrees. 
Since the total degree of the angles in a triangle are 180^o, we can write an equation:

60 + (22x + 4) + (15x + 5) = 180
60 + 4 + 5 + 22x + 15x = 180
69 + 37x = 180

37x = 111

x = 3

15x + 5 + 22x + 4 = 120

37x = 111

x = 3