Question

Divide 36 into two parts in such a way that 1/5 of one part is equal to 1/7 of the other. 

Answer 1

Two parts . one is x and another 36-x.  So  x +  (36 -x)  = 36
         1                          1
  x *  ---      =  (36 - x) * ----                 cross multiply 5 and 7, onto the other side
         5                        7

7 x  =    5 (36 - x)  =>  7 x = 180 - 5 x    =>  12 x = 180        x = 15
two partsare    15 and 21