Question

Află numărul X din egalitățile de mai jos:
a) (8x5+6x9+X):9+312=323.
b) 4x[(4xX-72):4+20]-64=20
c)100-[250:5x(X-5):5]X3=40
d) 643-[(X-162):5+159]=454
e) [(3xX+4)X2+5]X3+5=170.

Dau coroană, cinci stele, inima și 50 de puncte​

Answer 1

Răspuns:

Explicație pas cu pas:

a)

(8×5+6×9+X) : 9 + 312 = 323

( 40 + 54 + x ) : 9 = 323 - 312

( 94 + x ) : 9 = 11

94 + x = 11 × 9

94 + x = 99

x = 99 - 94

x = 5

__________________________

b)

4 × [(4 × X - 72) : 4 + 20] - 64 = 20

4 × [(4 × X - 72) : 4 + 20] = 20 + 64

4 × [(4 × X - 72) : 4 + 20] = 84

(4 × X - 72) : 4 + 20 = 84 : 4

(4 × X - 72) : 4 + 20 = 21

(4 × X - 72) : 4 = 21 - 20

(4 × X - 72) : 4 = 1

4 × x - 72 = 1 × 4

4 × x - 72 = 4

4 × x = 4 + 72

4 × x = 76

x = 76 : 4

x = 19

___________________________

c)

100 - [250 : 5 x (X - 5) : 5] × 3 = 40

[50 x (X - 5) : 5] × 3 = 100 - 40

[50 x (X - 5) : 5] × 3 = 60

50 x (X - 5) : 5 = 60 : 3

50 x (X - 5) : 5 = 20

50 x (X - 5) = 20 × 5

50 x (X - 5) = 100

x - 5 = 100 : 50

x - 5 = 2

x = 2 + 5

x = 7

_____________________

d)

643 - [( X - 162) : 5 + 159] = 454

( X - 162) : 5 + 159 = 643 - 454

( X - 162) : 5 + 159 = 189

( X - 162) : 5 = 189 - 159

( X - 162) : 5 = 30

x - 162 = 30 × 5

x - 162 = 150

x = 150 + 162

x = 312

__________________________

e)

[(3 × X + 4) × 2 + 5 ] × 3 + 5 = 170

[(3 × X + 4) × 2 + 5 ] × 3 = 170 - 5

[(3 × X + 4) × 2 + 5 ] × 3 = 165

(3 × X + 4) × 2 + 5 = 165 : 3

(3 × X + 4) × 2 + 5 = 55

(3 × X + 4) × 2 = 55 - 5

(3 × X + 4) × 2 = 50

3 × x + 4 = 50 : 2

3 × x + 4 = 25

3 × x = 25 - 4

3 × x = 21

x = 21 : 3

x = 7