Update line if a cell has specific value

Hi
I have a large sheet of data and some of the lines are corrupted, that is some of them are the right values multiplied by x2,x3 and so on.

Like you can see on the picture, lines 4 and 5 are just right but lines 3 and 7 are the original values multiplied by *2 and line 6 multiplied by *4.
What i want to do is to update lines 3 and 7 by divideing them by /2 and line 6 by /4
Best regards
HlynurCapture1.PNG