Answer
$f=11$
Work Step by Step
$f + 9 = 20$
In order to solve this algebraic equation, we will need to isolate the variable f on the L.H.S of the equation. We therefore subtract $9$ from both sides to eliminate the constants from the L.H.S as shown below:
$f + 9 -9 = 20 - 9$
Simplify to get:
$f = 11$
This shows that the equation has a possible solution at $f = 11$
Testing:
We replace for the variable $f$ with $11$ in the original equation as below:
$f + 9 = 20$
$11 + 9 = 20$
Simplifying, we have:
$20 = 20$
This proofs that the statement $f = 11$ is true.
