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[Substitution Method] (. )
. ()
. ()
() y .y = 5 − 3x ()
3x + 4(5 − 3x) = 11 ()
3x + 20 − 12x = 11 y
−9x = −9 .y x
.y = 5 − 3×1 = 2 x =1 x
y = 5 − 3x
.(x,y) = (1,2)
100 x 120
5 6.
. 9x + 6y
38% 8000
. 120x + 100y
.(100 ÷ 5 = 20 ) 120 ÷ 6 = 20
. 20(9x + 6y) = 180x + 120y