For this case, the first thing we must do is define a variable.
We have then:
x: unknown number
We now write the equation that models the problem:
[tex] (\frac{1}{2}) x + 15 = 9
[/tex]
From here, we clear the value of x.
We multiply both sides of the equation by 2:
[tex] (\frac{2}{2}) x + 2 (15) = 2 (9)
x + 30 = 18
[/tex]
We subtract 30 on both sides of the equation:
[tex] x + 30 - 30 = 18 - 30
x = -12
[/tex]
Answer:
The value of the unknown number is given by:
[tex] x = -12 [/tex]
