You have to make a equation like 15m+5m=1800 and substitute m for 150 (m for dollars per hour. or whatever letter you want) and solve from there
You have to multipied by two
While a credit card is usually better for short-term debt, a personal loan is often ideal for people who need more time to repay. Then again, which option is best for you may boil down to how much interest you'll pay, too.
Watch videos on YouTube, that's what I do with geometry.