how to make 1x from 50x

You need to use the formula

C1V1=C2V2
C=Concentration
V=Volume

Example

Make 20 ul of 1X restriction enzyme buffer from a 10X stock.

        10X stock *  X  =  1X stock *  20 ul

                     X = (1X stock *  20 ul) / 10X stock

                     X = 2.0 ul 10X stock
                       +18.0 ul of H2O