a) -3,6 - 4,7 = -8,3
б) 6,3 - (-8,1) = 6,3 + 8,1 = 14,4
в) $$4 \frac{1}{7} - 5 \frac{2}{7} = \frac{29}{7} - \frac{37}{7} = -\frac{8}{7} = -1 \frac{1}{7}$$
г) $$-6 \frac{5}{24} - (-5 \frac{13}{30}) = -6 \frac{25}{120} + 5 \frac{52}{120} = -1 + \frac{27}{120} = -\frac{93}{120} = -\frac{31}{40}$$