He would spend $46.57, I think(I am not that good with rounding)
For this case what you should know is that both functions are of the potential type.
We have then that
y = 2 * 2 ^ x This function grows exponentially upwards.
y = -2 * 5 ^ x This function grows exponentially downwards.
Answer See attached graphics.
The m in the equation is the slope and the y-intercept is the b.
y=1x-1
y=mx+b
Solve for x by cross multiplying and the answer is x=6
hope this helps and plz rate below :)
But it's not one doesn't always have to be the gcf