a) 3x+y=6 <=> y=6-3x <=> y=6-3x <=> y=6-3x <=>
2x+3y=11 <=> 2x+3(6-3x)=11 <=> 2x-18-9x=11 <=>
<=> y=6-3x <=> y=6-3 <=> y=6-3x <=> y=6-3x <=>
<=> -7x-18=11 <=> -7x=11+18 <=> -7x=29 <=> x=-29/7
<=> y=6-3-29/7 <=> y=-8/7
<=> x=-29/7 <=> x=-28/7
Mai departe trebuie sa le faci la fel.
P.S. este aplicatia photomath care te poate ajuta la astel de ecuatii.