Các bạn giải đáp hộ mình ,mình vote cho 5 sao

Đáp án:

Bài 1 :

1. Ta có : 

$\dfrac{13}{16}$ . $\dfrac{-29}{30}$  - $\dfrac{29}{30}$ .$\dfrac{27}{16}$  + $\dfrac{3}{16}$

=$\dfrac{-13}{16}$ . $\dfrac{29}{30}$  - $\dfrac{29}{30}$ .$\dfrac{27}{16}$  + $\dfrac{3}{16}$

= $\dfrac{29}{30}$ . ( $\dfrac{-13}{16}$ - $\dfrac{27}{16}$) + $\dfrac{3}{16}$

= $\dfrac{29}{30}$ . $\dfrac{-40}{16}$ +  $\dfrac{3}{16}$

= $\dfrac{-58}{24}$ + $\dfrac{3}{16}$

= $\dfrac{-116}{48}$ + $\dfrac{9}{48}$

= $\dfrac{-107}{48}$

2. Ta có : 

$ 1,25 . 2,5 . (-8) . (-4)$

$  =[1,25 . (-8)].[2,5 . (-4)]$

$ = (-10).(- 10) = 100$

Câu3

1. Ta có : 

$\dfrac{2}{3}$ . x - $\dfrac{4}{5}$ = $\dfrac{3}{4}$

<=> $\dfrac{2}{3}$ . x = $\dfrac{3}{4}$ + $\dfrac{4}{5}$

<=> $\dfrac{2}{3}$ . x = $\dfrac{31}{20}$

<=> x = $\dfrac{31}{20}$  : $\dfrac{2}{3}$

<=> x = $\dfrac{93}{40}$

2. Ta có : 

$(3x - 18) : 15 = -4$

$ <=> 3x - 18 = -60$

$ <=> 3x = -60 + 18$

$ <=> 3x = -42$

$ <=> x = -14$

3. Ta có : 

$\dfrac{-5}{6}$ - $\dfrac{1}{6}$ : x = $\dfrac{5}{12}$

<=> $\dfrac{1}{6}$ : x = $\dfrac{-5}{6}$ - $\dfrac{5}{12}$

<=> $\dfrac{1}{6}$ : x = $\dfrac{-5}{4}$ 

<=> x = $\dfrac{1}{6}$ : $\dfrac{-5}{4}$

<=> x = $\dfrac{-2}{15}$

4. Ta có : 

( $\dfrac{7}{8}$ - x ). $\dfrac{2}{3}$ = 4 

<=> $\dfrac{7}{8}$ - x = 4 : $\dfrac{2}{3}$

<=> $\dfrac{7}{8}$ - x = 6

<=> x = $\dfrac{7}{8}$ - 6 

<=> x = $\dfrac{-41}{8}$

Giải thích các bước giải: