12. fi 2(1)/(2)(-(3)/(4))= square

To solve the expression \(2\frac{1}{2} \left(-\frac{3}{4}\right)\), we first convert the mixed number to an improper fraction.<br /><br />\[ 2\frac{1}{2} = \frac{5}{2} \]<br /><br />Now, we multiply the two fractions:<br /><br />\[ \frac{5}{2} \times \left(-\frac{3}{4}\right) = \frac{5 \times (-3)}{2 \times 4} = \frac{-15}{8} \]<br /><br />So, the answer is:<br /><br />\[ \boxed{-\frac{15}{8}} \]