Răspuns :

Explicație pas cu pas:

[tex]$\mathbf{a) \frac{7}{15} - \frac{4}{15} - \frac{2}{15} = \frac{7}{15} - ( \frac{4}{15} + \frac{2}{15} ) }$[/tex]

[tex]$\mathbf{ - \frac{4}{15} - \frac{2}{15} = - ( \frac{4}{15} + \frac{2}{15} )}$[/tex]

[tex]$\mathbf{ - \frac{4}{15} - \frac{2}{15} = - \frac{2}{5} }$[/tex]

[tex]$\mathbf{ - \frac{2}{5} = - \frac{2}{5} \: \: egalitate \: adevarata }$[/tex]

[tex]$\mathbf{b) \frac{8}{15} - ( \frac{7}{15} - \frac{1}{15}) = \frac{8}{15} - \frac{7}{15} + \frac{1}{15} }$[/tex]

[tex]$\mathbf{ - ( \frac{7}{15} - \frac{1}{15}) = - \frac{7}{15} + \frac{7}{15} }$[/tex]

[tex]$\mathbf{ - \frac{2}{5} = - \frac{7}{15} + \frac{1}{15} }$[/tex]

[tex] - \frac{2}{5} = - \frac{6}{15} [/tex]

[tex]$\mathbf{ - \frac{2}{5} = - \frac{2}{5} \: \: egalitate \: adevarata}$[/tex]

[tex]$\mathbf{c)4 \frac{5}{9} - 2 \frac{1}{9} = (4 - 2) + ( \frac{5}{9} - \frac{1}{9}) }$[/tex]

[tex]$\mathbf{ \frac{36 + 5}{5} - \frac{18 + 1}{9} = 2 + \frac{4}{9} }$[/tex]

[tex]$\mathbf{ \frac{41}{5} - \frac{19}{9} = \frac{22}{9} }$[/tex]

[tex]$\mathbf{ \frac{274}{45} = \frac{22}{9} }$[/tex]

[tex]$\mathbf{274 \times 9 = 22 \times 45}$[/tex]

[tex]$\mathbf{2466 = 990 \: \: \: egalitate \: falsa}$[/tex]

Bafta!