What is x increased by 6

When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

David estimated he had about 20 fish in his pond. a year later, there were about 1.5 times as many fish. the year after that, the number of fish increased by a factor of 1.5 again. the number of fish is modeled by f(x)=20(1.5)^x. create a question you could ask that could be answered only by graphing or using a logarithm.