[tex]a)\\A = a\cdot b\cdot c \ \ /:ac\\\\b = \frac{A}{ac}[/tex]
[tex]b)\\X = \frac{1}{3}h(y+a) \ \ /\cdot3\\\\h(y+a) = 3X\\\\hy+ah = 3X\\\\hy = 3X-ah \ \ /:h\\\\y = \frac{3X-ah}{h}\\\\y = \frac{3X}{h}-a[/tex]
[tex]Zadanie\\\\a)\\b=?\\\\A=a\cdot b\cdot c\ \ \ \mid:(a\cdot c)\\\\\frac{A}{a\cdot c}=b\\\\ b=\frac{A}{a\cdot c}\\\\ Zal.\ a\ne0;\ c\ne0\\\\b)\\y=?\\\\X=\frac{1}{3}h(y+a)\ \ \ \mid \cdot 3;\ :h\\\\\frac{3X}{h}=y+a\ \ \ \mid-a\\\\ \frac{3X}{h}-a=y\\\\y=\frac{3X}{h}-a\\\\\ Zal.\ h\ne0[/tex]
