tolong jelasin aku ga ngerti

sudut CBD = CAB + ACB 
140 = (y+10)+(2y+10)
140 = 3y +20
140 - 20 = 3y
120 = 3y
y = 120 : 3
y = 40

jumlah seluruh sudut segitiga = 180
sudut CAB = y + 10 = 40 + 10 = 50
sudut ACB = 2y + 10 = 2(40)+10 = 90
sudut ABC = x

CAB+ACB+ABC = 180
50 + 90 + x = 180
140 + x = 180
x = 180-140
x = 40 (sudut ABC)

semoga membantu