a + b + c = 180
a + b = c + 70
a = b
2a + c = 180
2a = c + 70
2a + c = 180
2a - c = 70 | abziehen
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2c = 110
c = 55 °
2a + c = 180
2a + 55 = 180
2a = 125
a = 62.5 "
b = 62.5 "
Probe
a + b + c = 180
62.5 + 62.5 + 55 = 180
a + b = c + 70
6.5 + 62.5 = 55 + 70
125 = 125