Help with equation please

What is the 12th term of b(n)=-4-2(n-1)

In stepmber, daniel and justin opened a business. during their first three months of business, their average monthly profit was $51. if during their first month, they lost $29, and during their second month, they gained $115, what was their profit or loss for their third plzzz i will give you 299 points

If x varies directly as y, and x = 7.5 when y = 10, find x when y = 4