40oz glycol and water
10% is glycol
4oz is glycol
36oz is water
if glycol is to be added to make glycol 25% of all then
note: water does not change
100-25=75
water does not change so
36oz=75%
12=25%
there should be 12 oz of glycol total
4 now
12-4=8
8 oz should be added
sorry, I just wrote what I was thinking
answer is 8oz