" -20 + 5p - 7z " is not a question, and it doesn't beg for an answer.
It's an expression that stands for a number.
In order to determine what the number is, you need to know the
values of 'p' and 'z'. And if either of those changes, then the value
of " -20 + 5p - 7z " immediately changes too. So the whole thing is
a 'moving target'.
We want h(x) = g(x) - f(x).
h(x) = -2x + 9 -(6x - 5)
h(x) = -2x + 9 -6x + 5
h(x) = -8x + 14
1.6 cups of vinegar for 4 cups of soap.
i got:
n = -1 + 3/x
x = 3/n + 1
not sure if this helps but i hope it does somehow