Using new equipment, a worker finished 4 more parts in an hour than was planned and fulfilled his daily task not in 8 hours, but in 6 hours. how many parts did the worker have to finish during the day according to the schedule?

Let the planned number of parts per hour = x 
 Then the planned number of parts for the day = 8x 
 By finishing 4 more parts in an hour than was planned (x + 4) he fulfilled his daily task in 6 hours. 
 So he finished 6(x + 4) parts that day. 
 6(x + 4) = 8x 
 6x + 24 = 8x 
 2x = 24 
 x = 12