At the start of the shift your part counter reads 250 at the end of the shift the part counter reads 1075 how many parts did you produce

This can be mathematically expressed to

250 + X = 1075

where X represents the parts you produce before the shift ends

Transpose 250 to the other side by subtracting each side by 250

Thus, it goes like this

X = 1075 - 250

X = 825

You produced 825 parts in the middle of the shift.