Answer:
The answer is [tex]\beta =180-9x[/tex]
Step-by-step explanation:
Two angles are supplementary if the sum of their measures is 180°. That means that two angles, let's say, α, and its supplement, β, are supplementary if the following is true:
[tex]\alpha +\beta =180\\[/tex]
Now, let's say that α measures 9x degrees, and let us replace in the above expression:
[tex]9x +\beta =180\\[/tex]
If we now want to represent the measure of the supplementary angle, β, we have to subtract 9x from both sides of the expression to get the final algebraic expression of β in x:
[tex]\beta =180-9x[/tex]
Note that an algebraic expression is just a mathematical relationship between numbers and variables! The goal was to isolate the supplementary angle, β, and find its relationship with the variable x.