B2:

a) 79+243+21

=(79+21)+243

=100+243

=343

Tự luận

B1:

a) 45+132+ 355+68

=(45+355)+(132+68)

=400+200

=600

b) 36. 28+ 36.82+ 64. 69+64.41

= 36.(28+82) + 64.(69+41)

=36. 110 + 64. 110

= 110.(36+64)

=110.100

=11000

B2:

a) x+27=69

x=69-27

x=42

b) 24: (6-x) = 8

6-x=24 : 8

6-x=3

x=6-3

x=3

c) 9 . x - 13= 2² . 2³

9 . x - 13= $2^{5}$ 

9 . x - 13=32

9 . x =32 + 13

9 . x = 45

x = 45:9

x=5

B2:

a) 79+243+21

=(79+21)+243

=100+243

=343
b) (76+117)+(124-17)

=76+117+124-17

=(76+124)+(117-17)

=200+100

=300

B3:

a) x+19=27

x=27-19

x=8

b) 165-2.x=85

2.x=165-85

2.x=80

x=80:2

x=40

c) 160-160 : (18-x)=80

160 : (18-x)=160-80

160 : (18-x)=80

18-x=160:80

18-x=8

x=18-8

x=10

_______________________

B1

Không có kết quả đúng. Đáp án là $2^{2002}$ 

3) B

4) B

Tự luận
B1:
a) 45+132+ 355+68
=(45+355)+(132+68)
=400+200
=600
b) 36. 28+ 36.82+ 64. 69+64.41
= 36.(28+82) + 64.(69+41)
=36. 110 + 64. 110
= 110.(36+64)
=110.100
=11000
B2:
a) x+27=69

x=69-27

x=42

b) 24: (6-x) = 8

6-x=24 : 8

6-x=3

x=6-3

x=3