Your current schedule only lets you take two 1-credit courses every six months. you need 12 credits to get the degree you want. how long will it take you to get the degree?

So,

Since you can only take two one-credit courses every six months, you can earn 2 credits every six months, and 4 credits in one year.  Multiplying that by 3, you get 12 credits in 3 years.

It will take 3 years to get the degree.