Question

find 2 numbers whose sum is 29 and seven times difference is equal to four times of their sum?

Answer 1

X+y = 29
7(x-y)=4*29=116
7x-7y = 116
7x+7y=203
solving these two 
14x =319
x = 22.78
y= 6.22

Answer 2

find 2 numbers whose sum is 29 and seven times difference is equal to four times of their sum?
solution:
     let the numbers be x and y .
       therefore ,
                     x+y = 29  ............(  1 )(given)
                     7 (x-y) = 4 (x+y)  .......... (2) (given)
       From 1 and 2 , we get
                     7 (x - y) = 4 *29
                     7 (x -y) = 116
                     7x - 7y = 116  ............ (3)
                 multiply b/s of 1 by 7 , we get
                   7x + 7y = 203    ............ (4)
           Adding 3 and 4 , we get
                   14x = 319
                     x = 319 /14

substitute x in 1 , we get
                   319 /14 + y = 29
                                y = 29 -319/14
                                   = 29*14 - 319 /14
                                   =  406 - 319 /14
                                   = 87/14
hence  two numbers are
x=319/14 and y = 87/14

hope this helps you!!