91 is the product of greg’s age 7 .use variable g to represent greg’s age

I believe your equation will be: 7g = 91

The amount of passwords that Jina can make is only 12. Since the question says we are not allowed to use same letter twice that impacts the amount of passwords. In order to find the amount of passwords there is, we use the highest amount of letter choices, which is 4. Then the next letter can only have 3 letters. We can find out how many total passwords by doing 4*3 to get 12 different passwords.