x - cantitatea de mere a+b+c=x
a+b=2x/3
c=(a+b)-75⇒c=2x/3-75
a=3b-10⇒3b-10+b=2x/3⇒4b=2x/3+10⇒b=(2x/3+10)*1/4=2x/12+10/4
a=2x/3-b=2x/3-2x/12-10/4=8x/12-2x/12-10/4=6x/12-10/4
6x/12-10/4+2x/12+10/4+2x/3-75=x
8x/12+2x/3-x=75
8x/12+8x/12-12x/12=75
16x/12-12x/12=75
4x/12=75
x=12*75/4=225 cantitatea de mere
a=6*225/12-10/4=1350/12-30/12=1320/12=110 mere
b=2*225/12+10/4=450/12+30/12=480/12=40 mere
c=225-110-40=75 mere