Đáp án:

Giải thích các bước giải:

 1-(1/5+1/2)

=1-(2/10+5/10)

=1-7/10

=10/10-7/10

=3/10

6:2/3+4/7

=6×3/2+4/7

=9+4/7

=63/7+4/7

=67/7

Tìm x

X:4/5=5/2+1/3

X:4/5=15/6+2/6=17/6

X=17/6×4/5

X=34/15

3/9÷x=2/3-1/4

3/9÷x=8/12-3/12=5/12

X=3/9:3/12=1/3×12/3

X=4/3

8/5-3/7=41/35

2.3/4+4.1/7=319/28

1.6/5:3.3/5=11/18

3/5+9/4=57/20

BÀi 5

$\frac{3}{5}$ + $\frac{9}{4}$ 

= $\frac{12}{20}$ + $\frac{45}{20}$ 

= $\frac{57}{20}$

$\frac{8}{5}$ - $\frac{3}{7}$ 

= $\frac{56}{35}$ - $\frac{15}{35}$ 

= $\frac{41}{35}$

$2\frac{3}{4}$ x $4\frac{1}{7}$ 

= $\frac{11}{4}$ x $\frac{29}{7}$ 

= $\frac{319}{28}$

$1\frac{5}{6}$ : $3\frac{3}{5}$ 

= $\frac{11}{6}$ : $\frac{18}{5}$ 

= $\frac{11}{6}$ x $\frac{5}{18}$ 

= $\frac{55}{108}$ 

BÀi 6

1 - ( $\frac{1}{5}$ + $\frac{1}{2}$ )

= 1 - ( $\frac{2}{10}$ + $\frac{5}{10}$ )

= 1 - $\frac{7}{10}$

= $\frac{10}{10}$ - $\frac{7}{10}$

= $\frac{3}{10}$

6 : $\frac{2}{3}$ + $\frac{4}{7}$ 

= 6 x $\frac{3}{2}$ + $\frac{4}{7}$

= $\frac{18}{2}$ + $\frac{4}{7}$

= 9 + $\frac{4}{7}$

= $\frac{63}{7}$ + $\frac{4}{7}$

= $\frac{67}{7}$ 

BÀi 7

X : $\frac{4}{5}$ = $\frac{5}{2}$ + $\frac{1}{3}$

X : $\frac{4}{5}$ = $\frac{15}{6}$ + $\frac{2}{6}$ 

X : $\frac{4}{5}$ = $\frac{17}{6}$ 

X = $\frac{17}{6}$ x $\frac{4}{5}$ 

X = $\frac{68}{30}$

X = $\frac{34}{15}$

$\frac{2}{9}$ : X = $\frac{2}{3}$ - $\frac{1}{4}$ 

$\frac{2}{9}$ : X = $\frac{8}{12}$ - $\frac{3}{12}$  

$\frac{2}{9}$ : X = $\frac{5}{12}$

X = $\frac{2}{9}$ : $\frac{5}{12}$

X = $\frac{2}{9}$ x $\frac{12}{5}$

X = $\frac{24}{45}$

X = $\frac{8}{15}$