a) x · y + x · z = 150
x · ( y + z ) = 150
5 · ( y + z ) = 150
y + z = 150 : 5
y + z = 30
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b) a - b = 27 si c = 30
ca - cb = c × ( a - b ) = 30 × 27 = 810
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c) a + b = 4 si c = 5
5 a + 3 c + 5 b = 35
= 5 × ( a + b ) + 3 × 5 =
= 5 × 4 + 15 =
= 35