Tolong dong ini gimana caranya???

2][
Lingkaran
Keliling = 88 cm

a. r = ... ?
k = 88
2πr = 88
2 × 22/7 × r = 88
r = 88 × 7 / 44
r = 2 × 7
r = 14 cm

b.
Panjang busur MN
= 45°/360° × keliling
= 1/8 × 88
= 11 cm

3][
luas AOB/luas COD = sudut AOB/sudut COD
50/175 = 40/COD
COD = 40 × 175/50
COD = 4 × 35°
COD = 140°