-16/40 * 15/40

$${\mathtt{\,-\,}}{\frac{{\frac{{\frac{{\mathtt{16}}}{{\mathtt{40}}}}{\mathtt{\,\times\,}}\left({\frac{{\mathtt{15}}}{{\mathtt{40}}}}\right)}{{\mathtt{30}}}}}{{\mathtt{40}}}} = {\mathtt{\,-\,}}{\frac{\left({\mathtt{16}}{\mathtt{\,\times\,}}{\mathtt{15}}{\mathtt{\,\times\,}}{\mathtt{40}}\right)}{\left({\mathtt{40}}{\mathtt{\,\times\,}}{\mathtt{40}}{\mathtt{\,\times\,}}{\mathtt{30}}\right)}} = {\frac{{\mathtt{1}}}{{\mathtt{5}}}}$$

$${\mathtt{\,-\,}}{\frac{\left({\frac{{\mathtt{16}}}{{\mathtt{40}}}}\right){\mathtt{\,\times\,}}\left({\frac{{\mathtt{15}}}{{\mathtt{40}}}}\right)}{\left({\frac{{\mathtt{30}}}{{\mathtt{40}}}}\right)}} = {\mathtt{\,-\,}}{\frac{{\mathtt{1}}}{{\mathtt{5}}}} = -{\mathtt{0.2}}$$

We can multiply the numerator and denominator by 40 and we have:

(-16)(15)/30          notice that (15)/(30) = 1/2...so we have

(-16) (1/2)  =

-8