The nuts are $25.00 and he has a $5.00 coupon, so the nuts are on sale for $25-$5 = $<<25-5=20.00>>20.00
He eats 1 oz of nuts every evening and the bag has 40 oz of nuts, so it has 40/1 = <<40/1=40>>40 1 oz servings
The nuts cost $20.00 and there are 40 servings per bag, so his snack is $20/40 = $<<20/40=0.50>>0.50 per serving
#### 50