#### Answer

a. -11.1
b. $-\frac{1}{5}$
c. $\frac{3}{4}$

#### Work Step by Step

a. To subtract -2.7 - 8.4, add their absolute values and make the sum negative: 2.7 + 8.4 = 11.1, -11.1
b. $-\frac{4}{5} - (-\frac{3}{5})$ = $-\frac{4}{5} + \frac{3}{5}$ = $-\frac{1}{5}$
c. $\frac{1}{4} - (-\frac{1}{2}) = \frac{1}{4} + \frac{1}{2} = \frac{1}{4} + \frac{2}{4} = \frac{3}{4}$