a)=(3/4+3/12)+2/5

=1+2/15

=17/15

b)

(40/17-6/17)+(47/15-4/30)

=2+3=5

k cho minh

Tinh1 bằng cách thuận tiện nhất :

a ) 3/4 + 2/5 + 3/12

= 3/4 + 2/5 + 1/4 

= ( 3/4 + 1/4 ) + 2/5 

= 1 + 2/5 

= 2/5

b ) 47/15 + 40/17 - 4/30 - 6/17

= 47/15 + 40/17 - 2/15 - 6/17

= ( 47/15 - 2/15 ) + ( 40/17 - 6/17 )

= 45/15 + 34 /17

= 3 + 2 

= 5

tk mk nha 

thấy thế nào , comment đi

yêu mọi người nhiều lắm !!!

a)45/60+24/60+15/60=84/60=7/5                                                                                                                                                       b)(47/15-4/30)+(40/17-6/17)=(94/30-4/30)+34/17=90/30+2=3+2=5

Lời giải:

a. $\frac{3}{4}+\frac{2}{5}+\frac{3}{12}=\frac{3}{4}+\frac{2}{5}+\frac{1}{4}$

$=(\frac{3}{4}+\frac{1}{4})+\frac{2}{5}=1+\frac{2}{5}=\frac{7}{5}$

b. $\frac{47}{15}+\frac{40}{17}-\frac{4}{30}-\frac{6}{17}$
$=(\frac{47}{15}-\frac{4}{30})+(\frac{40}{17}-\frac{6}{17})$

$=(\frac{47}{15}-\frac{2}{15})+\frac{34}{17}$

$=\frac{45}{15}+\frac{34}{17}=3+2=5$

`5/17 xx 21/4 xx 47/15 xx 0`

`= (5/17 xx 21/4) xx  (47/15 xx 0)`

`= (5/17 xx 21/4) xx 0`

`=0`

9x4x198-6x18x17-36x47

= 7128-1836-1692

= 3600

Biểu thức trên ,ta được:

36*(198-3*17-47)=36*100=3600

3600 tk tui nhe

\(9\cdot4\cdot198-6\cdot18\cdot17-36\cdot47=36\cdot\left(198-47\right)-6\cdot18\cdot17\)

\(=6\cdot\left(6\cdot151\right)-6\left(18\cdot17\right)=6\cdot906-6\cdot306=6\left(906-306\right)=6\cdot600=3600\)

9 x 4 x 198 - 6 x 18 x 17 - 36 x 47

= 36 x 198 - 36 x 51 - 36 x 47

= 36 x (198 - 51 - 47)

= 36 x 100

= 3600  

Đáp án là : 3600

Tks Bạn Rất Nhiều

=15/17 x (4/7 + 3/7) - 1/3
=15/17 x 1 - 1/3
=15/17 x (3/3 - 1/3)
=15/17 x 2/3
=30/51

\(\frac{47}{53}\div\frac{17}{52}-\frac{47}{53}\times\frac{35}{17}\)

\(=\frac{47}{53}\times\frac{52}{17}-\frac{47}{53}\times\frac{35}{17}\)

\(=\frac{47}{53}\times(\frac{52}{17}-\frac{35}{17)}\)

\(=\frac{47}{53}\times\frac{17}{17}=\frac{47}{53}\times1=\frac{47}{53}\)