-9X + 9Y = 89
-8X - 9Y = - 73
................................
- 17X = 16
X = ( - 16\17)
...............................
- 9 * ( - 16\17) + 9Y = 89
9Y = 89 - 144\17
153\17Y = 1513\17 - 144\17
153Y = 1513 - 144
153Y = 1369
Y = 1369\153 = 8.94771 ( округляем до 8.9)
X = ( - 16\17) = ( - 0.941) ( округляем до - 0.9)