Răspuns: [tex]\bf \red{\dfrac{a\cdot b}{2}= \underline{21}}[/tex]
Explicație pas cu pas:
[tex]{\bf \dfrac{a}{6} = \dfrac{7}{b}} \xrightarrow[~egal~ cu~ produsul ~extremilor]{produsul~ mezilor~ e~ }~\bf a\cdot b=6\cdot7[/tex]
[tex]\bf a\cdot b=42\implies \red{\dfrac{a\cdot b}{2}} =\dfrac{42^{(2}~}{2} =\red{\underline{21}}[/tex]
