a) 35 x 2 x 9 x 5

= (35 x 9) x (2 x 5)

= (35 x 10 - 35) x 10

= (350 - 35) x 10

= 315 x 10 = 3150

b) 24 x 71 + 71 x 75 + 71

= 71 x (24+75+1)

=71 x 100

= 7100

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b, 53 + 45 + 135 + 147 + 50

= ( 53 + 147 ) + ( 45 + 135 ) + 50

= 200 + 180 + 50

= 200 + 330

= 530

b, 53 + 45 + 135 + 147 + 50

=(53+147)+(45+135+50)

=200+230

=430

\(\dfrac{75}{100}+\dfrac{3}{4}\times29+75\%\times30+0,75\times40\\ =\dfrac{75}{100}\times1+\dfrac{75}{100}\times29+\dfrac{75}{100}\times30+\dfrac{75}{100}\times40\\ =\dfrac{75}{100}\times\left(1+29+30+40\right)\\ =\dfrac{75}{100}\times100=75\)

\(\dfrac{75}{100}+\dfrac{3}{4}\) x 29 + 75% x 30 + 0,75 x 40

= 0,75 x 1 + 0,75 x 29 + 0,75 x 30 + 0,75 x 40

= 0,75 x (1 + 29 + 30 + 40)

= 0,75 x 100

= 75

= 25 x 75/100 + 75 x 0.92 + 25 x 0.25 + 75 x 8/100
= 25 x 0.75 + 75 x 0.92 + 25 x 0.25 + 75 x 0.08
= 25 x ( 0.75 + 0.25 ) + 75 x ( 0.92 + 0.08 )
= 25 x 1 + 75 x 1 
= ( 25 + 75 ) x 1 
= 100 x 1
= 100

537 × 39 - 537 × 29 = 537 × 39 - 29 = 537 × 10 = 5370

(5 x 5 x 36):9 + 450 - 100

=100+350=450

(25x36):9+450-75-25

= 900 : 9 + 450 - 75 -25

= 100 + ( 450 - 75-25)

= 100 + 350

= 450

450

=450