7/10-8/12+9/20 va rog sa ma ajutati cu aceasta problema cat de repede se poate!
mersi!

 

[tex]\displaystyle\\ \frac{7}{10}-\frac{8}{12}+\frac{9}{20}= ?\\\\ \text{cmmmc }= 60\\\\ \frac{7}{10}-\frac{8}{12}+\frac{9}{20}=\\\\ =\frac{6\times7}{60}-\frac{5\times8}{60}+\frac{3\times9}{60}=\\\\ =\frac{42}{60}-\frac{40}{60}+\frac{27}{60}=\\\\ =\frac{42-40+27}{60}=\boxed{\bf \frac{29}{60}}[/tex]

[tex] \frac{7}{10} - \frac{8}{12} + \frac{9}{20} = \frac{7}{10} - \frac{2}{3} + \frac{9}{20} = \frac{7 \times 6}{10 \times 6} - \frac{2 \times 20}{3 \times 20} + \frac{9 \times 3}{20 \times 3} = \frac{42}{60} - \frac{40}{60} + \frac{27}{60} = \frac{42 - 40 + 27}{60} = \frac{29}{60} [/tex]