Respuesta:
[tex]12x + 9y = 21 \: \: ( \times 8) \\ 96x + 72y = 168 \\ - 8x + 15y = 7 \: ( \times 12) \\ - 96x + 180y = 84 \\ 96x + 72y = 168 \\ - 96x + 180y = 84 \\ 252y = 252 \\ y = \frac{252}{252} = 1 \\ y = 1[/tex]
[tex]12x + 9y = 21 \\ 12x + 9 \times 1 = 21 \\ 12x + 9 = 21 \\ 12x = 21 - 9 \\ 12x = 12 \\ x = \frac{12}{12} = 1 \\ \\ x = 1[/tex]
Explicación paso a paso:
12x+9y=21
12*1+9*1=
=12+9=21
-8x+15y=7
-8*1+15*1=
-8+15=7
espero te sirva
