What is the letter ƒ in mathematics?

The letter f usually indicates that the equation is a function in the notation f(x). 

Example: f(x) = x + 1

It is a fancier/more proper replacement for the variable 'y'. The same is used for the letter g as in g(x) and h as in h(x). 

OR

It could just be a regular ole variable

Example: f + 1 = 7, solve for f

0.85 or 85%

step-by-step explanation:

1) divide 23 by 27

2) round the decimal to the nearest 10

3) so your answer would be 0.85 or 85%