According to the given from the first page please help on q

According to the given from the first page , please help on question C

With new MPN = 210 - 0.5N

So W = 210 - 0.5N

N = 300 + 8*(W)

N = 300 + 8(210 - 0.5N)

N = 300 + 1680 - 4N

5N = 1980

N = 1980/5 = 396

Change in N = 396-380 = 16

New W = 210 - 0.5*396

W = 210 - 198 = 12

Change in W = 12 - 10 = 2