80 is the fixed amount because it is a cost before you get their services. So basically the Y intercept. It is if you pay for an 80$ membership fee and then you are charged per month.
Both claims are false. In fact,
and
are one the multiplicative inverse of the other. This means, by definition of multiplicative inverse, that

So, it doesn't matter if
is positive or negative: the multiplication of one number and its inverse will always be 1: for example,

Similarly, when you multiply two number, the sign of the product depends on the sign of the factors as follows:
So, the multiplication of two negative numbers is a positive number.
OOOOH my favorite LONG DIVISION but anyways the answer is 164.4