How to solve the function 4y+x=12

If f(x)=x+7 and g(x)=1/x what is (fog)(x)

If f(x) = 4x - 3 and g(x) = x + 4, find (f - g) (x)

The unpaid balance on a mastercard charge was $1,056.23. during the month, payments of $300 and $250 were made and charges of $425 and $274.16 were added. if the finance charge is 1.2% per month on the unpaid balance, find the new balance at the end of the month. $1,205.39 $1,218.06 $918.06 $1,768.06