15.x=-75

x=-75:15

x=-5

3.|x|=18

x=18:3

x=6

suy ra x =6 hoặc -6

a,13.23+22-3.17+28

=299+22-3.17+28

=321-3.17+28

=318.17+28

=5406+28

=5434

b,-48+48.(-78)+48.(-21)

=[-48+48].(-78)+48.(-21)

=0.(-78)+(-1008)

=0+(-1008)

=(-1008)

16-5-16.24-5

=16-5-384-5

=11-384-5

=-373-5

=-378

Mr.Minh has some animals.He has two buffalo and two cows

5+5+(2+5+6)*5

​=5+5+13*5

​=5+5+45

​=55

​Vậy 5+5+(2+5+6)*5=55

1.How often are we going to stay there? 2.How often does Minh go swimming? 3.How often does your father go to work? 4.What does your father usually do in the morning?