Làm chi tiết giúp mình ạ, tính hợp lý nếu có thể ạ

17) ($\frac{1}{3}$ + $\frac{12}{67}$ + $\frac{13}{41}$) - ($\frac{79}{67}$ - $\frac{28}{41}$)

= $\frac{1}{3}$ + $\frac{12}{67}$ + $\frac{13}{41}$ - $\frac{79}{67}$ + $\frac{28}{41}$

= $\frac{1}{3}$ + ($\frac{12}{67}$ - $\frac{79}{67}$)+($\frac{13}{41}$ + $\frac{28}{41}$)

= $\frac{1}{3}$ + $\frac{-67}{67}$ + $\frac{41}{41}$

= $\frac{1}{3}$ + (-1) + 1

= $\frac{1}{3}$ 

 18) $\frac{38}{45}$ - ($\frac{8}{45}$ - $\frac{17}{51}$ - $\frac{3}{11}$)

= $\frac{38}{45}$ - $\frac{8}{45}$ + $\frac{17}{51}$ + $\frac{3}{11}$

= $\frac{2}{3}$ + $\frac{17}{51}$ + $\frac{3}{11}$

= $\frac{34}{51}$ + $\frac{17}{51}$ + $\frac{3}{11}$ = 1 + $\frac{3}{11}$

= $\frac{11}{11}$ + $\frac{3}{11}$ = $\frac{14}{11}$ = 1$\frac{3}{11}$ 

19) $\frac{7}{12}$ . $\frac{6}{11}$ + $\frac{7}{12}$ . $\frac{5}{11}$ - 2$\frac{7}{12}$

= $\frac{7}{12}$ . ($\frac{6}{11}$+$\frac{5}{11}$) - $\frac{31}{12}$

= $\frac{7}{12}$ . 1 - $\frac{31}{12}$ = -2

xin hay nhất đấy làm ơn <3