what is 3/7 times 4/5
$${\frac{{\mathtt{3}}}{{\mathtt{7}}}}{\mathtt{\,\times\,}}\left({\frac{{\mathtt{4}}}{{\mathtt{5}}}}\right) = {\frac{{\mathtt{12}}}{{\mathtt{35}}}} = {\mathtt{0.342\: \!857\: \!142\: \!857\: \!142\: \!9}}$$
Well, for fractions, the numerators multiply and the denominators multiply.
So it would be:
(3x4)/(7x5)
=12/35