pake caranya tolong

total sudut segitiga: 180°
sehingga
a. 90+2y+3y = 180
5y = 90
y = 18°
b. 5y+4y+3y = 180
12y = 180
y = 15°
c. 75+y+y = 180
2y = 105
y = 52,5°