x+50=75                                                  x-25=50

     x =75-50                                                 x =50+25

     x =25                                                       x =75

The number of people that have black hair is:

100% - 12% - 25% = 63%

There are: 600:100x63=378 ( people )

So the answer is 378 people have black hair.

Sorry! The result is too big!   

= 2023824

a) 34 numbers

b) 148

c) 1717

Bich Ngoc, You still lack!

11+22+33+44+...+999

=11(1+2+...+111)

=11+111+1/2x111/2

=34188

250+250=500

100+100+200+300+500+1000=2200

mk tk rồi đó nha

1000x100=100000

20+20=40

500.000+500.000=1.000.000

Is Cambodia.

k mk nha >_<  @_@  

10x10=100

mk tk bn rồi nhé

20+20=40

100x5=500

20+20=40

100+100=200

123456789+987654321=1111111110