a)
[tex]5d = \frac{2bp-cp}{3} \ \ \ |\cdot 3\\\\2bp-cp = 15d\\\\p(2b-c) = 15d \ \ \ |:(2b-c)\\\\\boxed{p = \frac{15d}{2b-c}}\\\\\\zal:2b-c\neq 0 \ \ \rightarrow \ \ 2b\neq c[/tex]
b)
[tex]O = \frac{3c-p}{U} \ \ \ |\cdot U\\\\OU = 3c-p\\\\\boxed{p = 3c-OU}\\\\\\Zal: \ U\neq 0[/tex]
c)
[tex]c = \frac{2-3r}{p} \ \ \ |\cdot p\\\\cp = 2-3r \ \ \ |:c\\\\\boxed{p = \frac{2-3r}{c}}\\\\\\Zal: p\neq 0 \ i \ c\neq 0[/tex]
