Rezolvati, prin metoda reducerii, urmatoarele sisteme de ecuatii liniare.

a) {x+2y=11 8x-2y=-2​

b) {x+3y=-10 -x+2y=-5

c) {2x-3y=7,5 5x-y=9

d) {2x+1=3y-7 3(x-y)+1=x+y-11

e) {6x+7y=4 -2x+9y=-24

f) {3x+11y=-1 -2x+9y+17