[tex]a) (-3 \frac{1}{2}+1 \frac{1}{5})+(-1\frac{1}{2}+2 \frac{9}{10})=(- \frac{7}{2}+ \frac{6}{5})+(- \frac{3}{2}+ \frac{29}{10})= (\frac{-35+12}{10})+\\+( \frac{-15+29}{10})= -\frac{23}{10}+\frac{14}{10}=-\frac{9}{10} \\
b) (-2 \frac{5}{45} )+(3 \frac{2}{5} -1 \frac{4}{15} )+(- \frac{7}{45})=- \frac{95}{45}+( \frac{17}{5}- \frac{19}{15})- \frac{7}{45}=- \frac{95}{45}+ \frac{32}{15}-\\-\frac{7}{45} = \frac{-95+96-7}{45}= -\frac{6}{45} =- \frac{2}{15} [/tex]