Răspuns:
Explicație pas cu pas:120/7
b) 9x=4y x=4y/9
2x+3y=40 2×4y/9+3y=40 8y+27y=360 35x=360
x=120/7 y=9x/4=9×120/7×4=270/7
c) 5x=3y x=3y/5
4y-3x=11/100 4y-3×3y/5=11/100 400y-180y=11 220y=11
y=1/20 x=3/20·5=3/100