$${\frac{{\mathtt{1}}}{{\mathtt{18}}}}$$ von 90 = $${\frac{{\mathtt{90}}}{{\mathtt{18}}}}$$ = 5
$${\frac{{\mathtt{5}}}{{\mathtt{18}}}}$$ von 90 = 5*5 = 25
$${\frac{{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{90}}}{{\mathtt{18}}}} = {\mathtt{25}}$$
$${\frac{{\mathtt{1}}}{{\mathtt{18}}}}$$ von 90 = $${\frac{{\mathtt{90}}}{{\mathtt{18}}}}$$ = 5
$${\frac{{\mathtt{5}}}{{\mathtt{18}}}}$$ von 90 = 5*5 = 25
$${\frac{{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{90}}}{{\mathtt{18}}}} = {\mathtt{25}}$$