1) 3 a + 5 b + 2 c = 176
= 3 × a + 3 × b + 2 × b + 2 × c =
= 3 × ( a + b ) + 2 × ( b + c ) =
= 3 × 28 + 2 × 46 =
= 84 + 92 =
= 176
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2) x · z + 7 · y · z + z = 63
z × ( x + 7 y + 1 ) = 63
z × ( 6 + 1 ) = 63
z × 7 = 63
z = 63 : 7
z = 9