Applicare la formula: $ab$$=ab$, dove $ab=2.5\cdot -3\cdot \left(\frac{4}{5}\right)$, $a=\frac{5}{2}$ e $b=-3$

Applicare la formula: $\frac{a}{b}c$$=\frac{ca}{b}$, dove $a=4$, $b=5$, $c=-\frac{15}{2}$, $a/b=\frac{4}{5}$ e $ca/b=-7.5\cdot \left(\frac{4}{5}\right)$

Applicare la formula: $ab$$=ab$, dove $ab=-7.5\cdot 4$, $a=-\frac{15}{2}$ e $b=4$

Applicare la formula: $\frac{a}{b}$$=\frac{a}{b}$, dove $a=-30$, $b=5$ e $a/b=-\frac{30}{5}$