tolong di jawab! yh! please!

nomor a
[tex]4x + 90 + 2x = 180 \\ 6x + 90 = 180 \\ 6x = 180 - 90 \\ 6x = 90 \\ x = \frac{90}{6} \\ x = 15[/tex]

nomor b
sudut BOC siku" = 90°

nomor c
sudut AOB = 4x = 4.15 = 60°

nomor d
Sudut COD = 2x = 2.15 = 30°