15x20-15x10+15x40=750

tck nhaaaaaaaa

15 x 20 - 15 x 10 + 15 x 40

= 15 x ( 20 - 10 + 40 )

= 15 x 50

= 750

10x20-15x10+15x40

=650

tíc mình nha

mình nhanh nhất đó

(-15)\(x\) = - 45

       \(x\)  = - 45 : (-15)

      \(x\)  = 3

Vậy \(x=3\)

(-15)\(x\) = 10.(-40).(-5)

    -15\(x\)  =  -400.(-5)

   -15\(x\)   = 2000

    \(x\)   = 2000 : (-15)

    \(x\)  = - \(\dfrac{400}{3}\)

Vậy \(x=-\dfrac{400}{3}\) 

(+2).\(x\)  = - 16

      \(x\)   = -16 : (2)

      \(x\)  = - 8

Vậy \(x=-8\)

a) 15 cm2 + 20 cm2 = 35 cm2

60 cm2 - 42 cm2 = 18 cm2

20 cm2 + 10 cm2 + 15 cm2 = 45 cm2

b) 12 cm2 x 2 = 24 cm2

40 cm2 : 4 = 10 cm2

50 cm2 - 40 cm2 + 10 cm2 = 20 cm2

x + 15 = 40 -10

x        = 30 - 15

x       = 15

x+15=30

      x=30-15

      x=15

Vậy:x=15

k đi 

k lại

Tìm x:

x+15=40-10

x=30-15=15

ai k mik mik sẽ k lại !!!!!!!!@#$%^&8a9

3 x 15 + 21 x 15 + 85 x 5

= 45 + 315 + 425

= 785

15 - 30 + 40 

= 25

21 + 19 - 50 + 10

= 0

\(\dfrac{1}{5}-\dfrac{1}{4}+2\)

\(=-\dfrac{1}{20}+2\)

\(=\dfrac{39}{20}\)

\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)

\(=\dfrac{5}{12}\times\dfrac{1}{4}\)

\(=\dfrac{5}{12}\times\dfrac{3}{12}\)

\(=\dfrac{5}{48}\)

\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)

\(=-\dfrac{9}{20}\)

\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)

\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)

\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)

\(\dfrac{1}{5}-\dfrac{1}{4}+2\)

\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)

\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)

\(=\dfrac{44}{20}-\dfrac{5}{20}\)

\(=\dfrac{39}{20}\)

\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)

\(=\dfrac{5}{12}\times\dfrac{1}{4}\)

\(=\dfrac{5}{48}\)

\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)

\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)

\(=\dfrac{6}{20}-\dfrac{15}{20}\)

\(=-\dfrac{9}{20}\)

Help meeeeeeeeeee