the orange line goes up by $3 and the red line goes up by $6.75 at what cost will it be the same for both.

The orange line will go past the page so will the red 1

Here, Line drawn in bottom is Orange with the slope of "three" and line drawn above than that is Red with slope, 6.75

As the initial value (Original point of testing) of Red line is Greater than the Orange and it's slope is also greater, the two lines will never meet up to each other.

Hope this helps!