I need a answer for this problem

The answer would be f(x)=3.9n+15.85 since every floor is 3.9 meters high you need to multiply 3.9 by the number of floors which in this case would be n. Then you add the height of the antenna because it is included in the measurement. Using the order of operations you would multiply from right to left first which would give you the height of the building without the antenna, then you would add the 15.85 which would give you the total height of the building including the antenna if you would know how many floors there are.

So radio antena is 15.85, this doesn't change with the number of floors (number of floors is the only variable)
each floor is 3.9 meters, so 3.9 times number of floors
function is f(n)=3.9n+15.85
( just for fun it can be simplified into f(n)=3.9(n+4.0641))

the function is f(n)=39n+15.85

second problem
domain is the set of numbers you can put into the function

range is the set of numbers you get from the numbers in the domain when put into the function (like the solution or result)

so if x=-7 then f(x)=-9
the range is obviously all the numbers on the right
range=-9,-4,-1

answers:
18:  f(n)=3.9n+15.85
19:  range=-9,-4,-1

Let's say you're being asked to solve for y and the problem looks like this: 16x+4y=20. Basically what's being asked here is to get all the numbers on the other side of the equal sign so that y is by itself, i.e. y=(all the other things you've put on the other side of the equal sign).

Begin by subtracting the number that's being added to 4y. In this case that number would be 16x (the variable, x, goes with it the number too, remember that) So after you've subtracted 16x your problem should look like this:

4y=20-16x

Now you've made the problem a bit easier. It might look like you're done but ask yourself, "Is y totally by itself?" No it is not, there's a 4 clinging to it! So now we need to get 4 to the other side of the equal sign as well which will finally leave y by itself.

What you'll need to do now is divide the 4 into both side of the equation. The 4/4 in front of the y's will cancel out and become 1y (at this point, the 1 turns invisible so that all you'll see is y, the one will always be there, but consider it invisible). So now all you have to do is divide 4 into 20+16x. You will get: y=5-4x

And now your problem is solved. You've not only gotten all the other numbers to the other side of the equal sign, but you've reduced those numbers by dividing them by 4.