(dấu chấm là dấu nhân nha e)

 *\(\dfrac{1}{2}\). \(\dfrac{1}{4}\)+\(\dfrac{3}{4}\)

= \(\dfrac{1}{8}\)+\(\dfrac{3}{4}\)

= \(\dfrac{1}{8}\)+\(\dfrac{6}{8}\)= \(\dfrac{7}{8}\)

 *\(\dfrac{3}{4}\).\(\dfrac{5}{6}\).\(\dfrac{8}{15}\)

= \(\left(\dfrac{3}{4}.\dfrac{8}{15}\right)\).\(\dfrac{5}{6}\)

= \(\dfrac{2}{5}\).\(\dfrac{5}{6}\)

= \(\dfrac{1}{3}\)

 *\(\dfrac{12}{19}\): \(\dfrac{17}{38}\).\(\dfrac{16}{9}\)

= \(\dfrac{12}{19}\). \(\dfrac{38}{17}\).\(\dfrac{16}{9}\)= 2,5

1/8+3/4=7/8

5/8x8/15=1/3

24/17x16/9=128/51

1/2x1/4+3/4=7/8

3/4x5/6x8/15=1/3

12/19:17/38x16/9=128/51

1/8+3/4=7/8

5/8x8/15=1/3

24/17x16/9=128/51

\(x\times282-270\times x=1512\\ x\times\left(282-270\right)=1512\\ x\times12=1512\\ x=1512:12\\ x=126\)

x = 126

x×282−270×x=1512

x×(282−270)=1512

x×12=1512

x=1512:12

x=126

a) ( 36 x 28 + 36 x 45 ) : 73

= 36 x (28 + 45 ):73

=36 x 73 :73

= 36 x (73 : 73)

= 36 x 1

= 36

b) ( 98 x 17 - 26 x 17 ) : 72

= 17 x (98-17):72

= 17 x 72 :72

=17 x (72 :72)

= 17 x 1

= 17

a) ( 36 x 28 + 36 x 45 ) : 73 = 36 

b) ( 98 x 17 - 26 x 17 ) : 72 = 17 

Bạn phải giải hẳn ra

117 x 36 + 117 x 72 - 17 x 72 - 17 x 36

= ( 117 - 17 ) x 36 - ( 117 - 17 ) x 72

= 100 x 36 - 100 x 72

= 100 x ( 36 - 72 )

= 100 x -36

 = -3600

____________________________________

408 x 53 - 5 x 204 - 204

= 408 x 53 - 5 x 204 - 204 x 1

= 408 x 53 - ( 5 - 1 ) x 204

= 408 x 53 - 4 x 204

= 21624 - 816

= 20808

Cảm ơn bạn Đinh Chí Công

Phương pháp giải:

Muốn tìm số bị trừ ta lấy hiệu cộng với số trừ.

Lời giải chi tiết:

a) x − 3 = 9

    x = 9 + 3

    x = 12

b) x − 8 = 16

    x = 16 + 8

    x = 24

c) x − 20 = 35

    x = 35 + 20

    x = 55

d) x − 5 = 17

    x = 17 + 5

    x = 22

e) x − 15 = 27

    x = 27 + 15

    x = 42

g) x − 36 = 36

    x = 36 + 36

    x = 72

 = 117 x 100 - 17 x 100

= ( 117 - 17 ) x 100

= 100 x 100

= 10000

117 x 100 - 17 x 100

=(117 - 17) x 100

= 100 x 100

= 10 000

49439808/11

\(=\dfrac{36\cdot22\cdot51}{11\cdot17\cdot72}=\dfrac{1}{2}\cdot3\cdot2=3\)