[tex]\frac{1}{5} +(\frac{3}{20} - \frac{1}{12} ) -(\frac{5}{6} - \frac{49}{60} )=[/tex]
= [tex]\frac{1}{5} +(\frac{9}{60} -\frac{5}{60})-(\frac{50}{60}-\frac{49}{60})[/tex]
= [tex]\frac{12}{60} +\frac{4}{60} -\frac{1}{60}[/tex]
= [tex]\frac{15}{60}[/tex] = [tex]\frac{1}{4}[/tex]