-7b=7/8 -2w=-1/2

-7b=7/8 /*8 -56b=7 /: 56 b= 7/56= 1/8 -2w=-1/2 /*2 -4w=-1 /:(-4) w=1/4

-7b=7/8 /(*-1/7) b=-7/56=-1/8 -2w=-1/2 /(*-1/2) w=1/4