[tex]\bf \cfrac{2}{9}\times a=\cfrac{3}{15}\implies \cfrac{2a}{9}=\cfrac{1}{5}\implies 2a=\cfrac{9\cdot 1}{15}\implies 2a=\cfrac{3}{5}
\\\\\\
a=\cfrac{3}{2\cdot 5}
\implies
a=\cfrac{3}{10}\\\\
-------------------------------\\\\
\cfrac{2}{5}\times b=\cfrac{7}{12}\implies \cfrac{2b}{5}=\cfrac{7}{12}\implies 2b=\cfrac{5\cdot 7}{12}\implies 2b=\cfrac{35}{12}
\\\\\\
b=\cfrac{35}{2\cdot 12}\implies b=\cfrac{35}{24}[/tex]
