a.a+b=31.5 a=8b 8b+b=31.5 9b=31.5 b=3.5 a=8*3.5 a=28 b.a+b=51.66 a:b=7.5=>a=7.5b 7.5b+b=51.66 8.5b=51.66 b=6.07 a=7.5*6.07=45.58 c.a-b=30.8 b=a/12 a-a/12=30.8 Inmultim cu 12 12a-a=369.6 11a=369.6 a=33.6 b=33.6/12=2.8 d.a*b=40 a=2.5b 2.5b*b=40 2.5b**2=40 b**2=16 b=+-radical din 16  b1=+4 b2=-4 a1=2.5*4=10 a2=2.4*(-4)=-10 e.a*b=80 b=a/3.2 a*a/3.2=80 a**2/3.2=80 a**2=80*3.2 a**2=256 a=+-radical din 256 a1=16 a2=-16 b1=16/3.2=5 b2=16/(-3.2)=-5