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:
\((\frac{1}{2}) x + 15 = 9
\)
From here, we clear the value of x.
We multiply both sides of the equation by 2:
\((\frac{2}{2}) x + 2 (15) = 2 (9)
x + 30 = 18
\)
We subtract 30 on both sides of the equation:
\(x + 30 - 30 = 18 - 30
x = -12
\)
Answer:
The value of the unknown number is given by:
\(x = -12\)
