[tex]Zadanie\ 5c\\\\h=12\\\\Ob.=42\\\\2x+1+x+1+3x+1+4x-1=42\\\\10x+2=42\ \ \ \mid-2\\\\ 10x=40\ \ \ \mid:10\\\\x=4\\\\P=\frac{1}{2}\cdot a\cdot h\\\\a=2x+1+x+1= 2\cdot4+1+ 4+1=14\\\\P=\frac{1}{2}\cdot14\cdot12=7\cdot12=84\ (j^{2})\\\\Zadanie\ 6b\\\\\frac{1}{2}\cdot(6-2a)=2\cdot(3a-1)+7\\\\3-a=6a-2+7\ \ \ \mid-3\\\\-a=6a+2\ \ \ \mid-6a\\\\-7a=2\ \ \ \mid:(-7)\\\\a=-\frac{2}{7}[/tex]
