Question 133082
Not sure I understand the question, but will answer based on the model being
{{{f(x)=6.75x+12}}}  If that model is wrong, please just fix it and then use steps like the ones below to solve using the corrected model.

Given: {{{f(x)=6.75x+12}}} is a model for student loans x years after 1993 (in Billions).

What year will the expected loan amount be 39Billion?

We have a model that is a function. The value of X is the number of years since 1993. The model yields he expected loan amount for that specific year.

In this problem, we are given the model and the loan amount. we are asked to find the year.

{{{f(x)=6.75x+12}}}
{{{39 = 6.75x+12}}}
{{{27 = 6.75x}}}
{{{4 = x}}}

So, four years after 1993, the loan will be $39B. 
The answer is 1993 + 4 = 1997