[tex] \frac{9}{4}- \frac{3}{4}= \frac{9-3}{4}= \frac{6}{4}= \frac{3}{2} [/tex]
[tex] \frac{6}{7}- \frac{1}{2}= \frac{12}{14}- \frac{7}{14}= \frac{5}{14} [/tex]
[tex] \frac{3}{4}+ \frac{2}{5}- \frac{1}{3}= \frac{90}{120}+ \frac{48}{120} - \frac{40}{120}[tex]= \frac{98}{120} [/tex]