Question 33127
First try to form equations based on the questions.
1. let X be the number of computer A and Y be the number the number of computers B 

2.Now u know the total number of computers u r planning to buy..that is 16.

so the first euation would be X + Y = 16.

3. Now,try to form another equation with the help of the costs.
 that is,   700 * X + 500 * Y = 10,000 ( THE TOTAL AMOUNT U R GOIN TO SPEND IS 10,000).So we've got 2 equations and now it is easy to solve the problem..

write the 2 equations:

 EQ.1    700 * X + 500 * Y = 10,000
 EQ.2         X +        Y = 16

Now multiply the  whole eq.2 by -500(always try to make the  co-efficient of EITHER X OR Y in both equations to be the same with opposite sign,here we r tryin to make co-efficient of Y SAME ,BUT WITH OPPOSITE SIGN,THAT IS -500) ,and u'll get eq.2 as

  
 new EQ.2       -500 * X -500 * Y  = -8000 ,(this is done to solve the 2 equations and find X & Y)

NOW ADD EQ .1 AND THE NEW EQ.2.
We get ,

200 * X = 2000  (+500X -500X GET CANCELLED)
SO X = 2000/200
     = 10.
WE KNOW THAT X + Y = 16,THEREFORE
             10 + Y = 16 AND Y = 16- 10 

                  Y= 6.
SO THE VALUES ARE NUMBER OF COMPUTER A IS 10 AND COMPUTER B IS 6.

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