[tex]P=\frac12ah[/tex]
[tex]a)\\P=\frac12\cdot3\cdot4=\frac12\cdot5\cdot a\\\frac12\cdot3\cdot4=\frac12\cdot5\cdot a\\\frac32\cdot4=\frac52a\\6=\frac52a|:\frac52\\a=6:\frac52=6\cdot\frac25=\frac{12}{5}=2\frac25[/tex]
[tex]b)\\P=\frac12\cdot9\cdot5=\frac12\cdot7\cdot b\\\frac12\cdot9\cdot5=\frac12\cdot7\cdot b\\\frac92\cdot5=\frac72\cdot b\\\frac{45}2=\frac72b|:\frac72\\b=\frac{45}2:\frac72=\frac{45}2\cdot\frac27=\frac{45}7=6\frac37[/tex]
[tex]c)\\P=\frac12\cdot5\cdot3=\frac12\cdot c\cdot2\\\frac12\cdot5\cdot3=\frac12\cdot c\cdot2\\\frac52\cdot3=c\\c=\frac{15}2=7\frac12[/tex]
