You can 
put this solution on YOUR website! .
Writing such system is easy, standard and routine task
       x  +     y = 280  liters     (1)     (total volume)
    0.25x + 0.20y =  61  liters     (2)     (amount of "real fruit juice")
In this system, x is the volume of the 25% juice (drink A), and
                y is the volume of the 20% juice (drink B).
Your request is satisfied: the requested system of equations is written.