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swmoga membantu.............

gambar 1 (90°)
3a+2a = 90
5a =90
a = 90÷ 5
a = 18

gambar 2 (180°)
46 + (a+29) + (5a+15) = 180
46 +29+15+a+5a = 180
90 + 5a = 180
5a =180- 90
5a = 90
a = 18