Page 115 - aljaber

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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