To calculate blood alcohol concentration, we need to know Josh's gender, body weight, when he started drinking, when he stopped drinking, and how many "standard" drinks of alcohol he drank. Then, we plug this information into the formula:
[(# of standard drinks/2) x (gender constant/body weight (lbs))] - (.017 x hours)
Josh is a male, so the gender constant is .73 (for females, the constant would be .66).
Josh is 172 lbs.
The wedding reception went from 8pm to midnight, so Josh was drinking for 4 hours.
1 martini is close to 2 standard drinks, 1 glass of wine is close to 1.3 standard drinks, 1 glass of champagne is close to 1.4 standard drinks, and 1 tequila shot is close to 1 standard drink. Since Josh had 2 martinis, 3 glasses of wine, 2 glasses of champagne, and 4 tequila shots, he drank about 14.7 standard drinks.
[(14.7/2) x (.73/172)] - (.017 x 4)]
[7.35 x .0042 - .068]
[.03087 - .068] = -.0407
Alex's back is .04%.