Răspuns:
Explicație pas cu pas:
a + b = 14
b + c = 9
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2a + 5b + 3c = ?
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a + b = 14 | × 2
2a + 2b = 28
b + c = 9 | × 3
3b + 3c = 27
______________ +
2a + 2b + 3b + 3c = 28 + 27
2a + 5b + 3c = 55
a+b=14/×2=>2a+2b=28 ^
b+c=9/×3=>3b+3c=27 | +
=>2a+(2b+3b)+3c=28+27
2a+5b+3c=55