769 km in 3 zile
a+b+c=769 km
a+b=516 km
b+c=620 km ⇒ b = 620--c
a = 516 - b = 516 - 620 + c = c - 104
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516 - 620 + c + 620 - c + c = 769
516+c=769
c=769-516=253 km a 3-a zi
b=620-257=363 km a 2-a zi
a=257-104=153 km prima zi
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Verificare: a+b+c= 253+363+153 = 769 km, corect,
a+b=153+363=516, corect.
