Cerinta: Sa se calculeze: ( a + c ) × ( 3 a + 2 b + 3 c ).
a + b + c = 18
2 a + b + 2 c = 25
( a + b + c ) + ( a + c ) = 25
18 + ( a + c ) = 25
a + c = 25 - 18
a + c = 7
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( a + c ) × ( 3 a + 2 b + 3 c ) = 301
= 7 × [ ( a + b + c ) + ( 2 a + b + 2 c ) ] =
= 7 × ( 18 + 25 ) =
= 7 × 43 =
= 301