How do you find the value of $x$ so that the function $n(x) = 7x + 4$ has the given value 39?

Hint: As we observe that the given equation is a linear equation, which we can solve by taking the variable on the left side and all constant on the right side then perform simplification operations to get the value of the given variable.

Complete step by step solution:
As per the question, we have $n(x) = 7x + 4 = 39$
$7x + 4 = 39$
We will take variable one left-hand side and constant on the right-hand side of the equation, as we take +4 on the right-hand side and it will become -4
$7x = 39 - 4$
$7x = 35$
As the above equation, 7 is multiplied with $x$ so, it will divide on the right-hand side.
$x = 5$

Hence, the value of $x$ is 5.

Note:
We should remember that if we have an equation with one variable then the equation is a linear equation that is easily solved by keeping variables on one side and constant on another side of the equation. When we will change the side of variables and constants, signs will also change.