We need to find the number of ounces of 1% hydrocortisone and 5% hydrocortisone the pharmacist should use to make a 7-ounce tube with a concentration of 2% hydrocortisone.
Let's call x the number of ounces of 1% hydrocortisone, and y the number of ounces of 5% hydrocortisone.
Then, 1% of x added to 5% of y must result in 2% of 7:
Also, we have:
Then, using the above result in the first equation, we obtain:
Now, using this result back in the second equation, we obtain:
Therefore, the answers are: