When a new smart phone is invented and sold, its value decreases over time because it wears down and because newer technology is developed to replace it.

Suppose the current value of a new phone is $\$ 750$ and its value is expected to decrease $12 \%$ every year. Define a function, $g$, which expresses the value of the device in terms of the varying number of years, $t$, that have passed since it was released.
\[
\begin{array}{l}
g(t)=750(1.12)^{t} \\
g(t)=750-90 t \\
g(t)=750+90 t \\
g(t)=750(0.88)^{t} \\
g(t)=750(0.12)^{t}
\end{array}
\]

Step 1 ：Define a function, $g$, which expresses the value of the device in terms of the varying number of years, $t$, that have passed since it was released.

Step 2 ：Consider the following functions: \n\[\begin{array}{l}g(t)=750(1.12)^{t} \g(t)=750-90 t \g(t)=750+90 t \g(t)=750(0.88)^{t} \g(t)=750(0.12)^{t}\end{array}\]

Step 3 ：The value of the phone decreases by 12% every year. This means that every year, the phone retains 88% of its value from the previous year.

Step 4 ：Therefore, the function that describes the value of the phone over time is $g(t) = 750(0.88)^t$.

Step 5 ：\(\boxed{g(t) = 750(0.88)^t}\) is the final answer.