[tex]\underline{Sposob \ 1}\\\\a = 7 \ cm\\\\h_{a} = 12 \ cm\\\\P = \frac{1}{2}a\cdot h_{a} = \frac{1}{2}\cdot7\cdot12} = \boxed{42 \ cm^{2}}[/tex]
[tex]\underline{Sposob \ 2}\\\\b = 15 \ cm\\\\h_{b} = 5,6 \ cm\\\\P = \frac{1}{2}b\cdot h_{b} = \frac{1}{2}\cdot15\cdot5,6 = \boxed{42 \ cm^{2}}[/tex]
[tex]\underline{Sposob \ 3}\\\\c = 20 \ cm\\\\h_{c} = 4,2 \ cm\\\\P = \frac{1}{2}c\cdot h_{c} = \frac{1}{2}\cdot20\cdot4,2 = \boxed{42 \ cm^{2}}[/tex]
