x + 3 y = 2 y + z = 14
a) x + 5 y + z = x + 3 y + 2 y + z = 14 + 14 = 28
b) 3 x + 15 y + 3 z = 84
= 3 x + 9 y + 6 y + 3 z =
= 3 ( x + 3 y) + 3 ( 2 y + z ) =
= 3 × 14 + 3 × 14 =
=42 + 42 =
= 84
c) 5 x + 11y - 2 z =
= 5 x + 15 y - 4 y - 2 z =
= 5 ( x + 3y ) - 2 ( 2 y + z) =
=5 × 14 - 2 × 14 =
= 70 - 28 =
= 42
d) 5 x + 19 y + 2 z = 98
= 5 x + 15 y + 4 y + 2 z =
= 5 ( x + 3 y ) + 2 ( 2 y + z) =
= 5 × 14 + 2 × 14 =
= 70 + 28 =
= 98
