take the f function minus the g function and subtract like terms
4 - (-2) is 6, so that part is 6*8 to the x power,
then you have the 18x with nothing subtracted from it,
and then -7 - -12....or at least that looks like -12...hard to see with it being covered up...anyway that part would be 5.
so 6*8^x + 18x + 5 is the answer
