a)
[tex]7+3\sqrt{5}-2-1,5\sqrt{5}=5+3\sqrt{5}-1,5\sqrt{5}=5+1,5\sqrt{5}[/tex]
b)
[tex]4(5+3\sqrt{2})-3(\sqrt{2}+7)=20+12\sqrt{2}-3\sqrt{2}-21=-1+12\sqrt{2}-3\sqrt{2}=-1+9\sqrt{2}[/tex]
c)
[tex]3(3\sqrt{9}-4)-2(3\sqrt{9}-7)=3(3*3-4)-2(3*3-7)=3(9-4)-2(9-7)=3*5-2*2=15-4=11[/tex]
