Jika 3x-2y=8 Dan 12x+3y=21 Maka 2x-3y adalah.... a.-7 b.-1 c.1 d.7 Mohon jawab beserta cara mengerjakannya yaa

jawabannya B. 7…………………

2x - 3y = ....?

3x - 2y = 8 (×3)
12x + 3y = 21 (×2)

==> ( 9x - 6y = 24) + (24x + 6y = 42)
==> 33x = 66
==> x = 66 : 33
==> x = 2

( x = 2 ) ==> 12x + 3y = 21
==> 12(2)+3y = 21
==> 24 + 3y = 21
==> 3y = 21 - 24
==> 3y = -3
==> y = -1

( x = 2, y = -1 )
==> 2x - 3y
==> 2(2)-3(-1)
==> 4 + 3
==> 7