Answer :
[tex]c=[(3+6+9+...+300):303]-40 \\\\ c=[3(1+2+3+...+100):303]-40 \\\\ c=[3*\frac{(1+100)*100}{2}:303]-40 \\\\ c=(3*101*50:303)-40 \\\\ c=(303*50:303)-40 \\\\ c=50-40 \\\\ \boxed{c=10}[/tex] [tex]3a-2b=b-2a+3c \\\\ 3a-2b=b-2a+3*10 \\\\ 3a+2a=b+2b+30 \\\\ 5a=3b+30 \\\\ \boxed{a=\frac{3b+30}{5}}[/tex]
[tex]5a-3(b+c)+145:5-8= \\\\ 5a-3(b+10)+29-8= \\\\ 5*\frac{3b+30}{5}-3b-30+21= \\\\ =3b+30-3b-30+21= \\\\ =30-30+21= \\\\ =\boxed{\boxed{21}}[/tex]
[tex]5a-3(b+c)+145:5-8= \\\\ 5a-3(b+10)+29-8= \\\\ 5*\frac{3b+30}{5}-3b-30+21= \\\\ =3b+30-3b-30+21= \\\\ =30-30+21= \\\\ =\boxed{\boxed{21}}[/tex]
