You can multiply 6.25 by 2 (which is 12.5) to find how much money he had before he bought the sandwich. Then you can find how much money he had before buying the DvD by multiplying 12.5 by 8/3 which is 33.33 dollars. Therefore Jake started with 33.33 dollars.
(you can prove this since 3/8 of 33.33 is 12.5 and 1/2 of that is 6.25)
I hope this helps. Let me know in the comments if anything is unclear.
If the point ( 8,-2) is on F(X) that a point ( -2,8) must be on the graph of the inverse fraction F^-1 (x) because the invers of a function is found by inversing the coordinate x and y.
Use pemdas to answer this question.
Parenthesis
Exponents
Multiply or
Divide (whichever comes first)
Add or
Subtract (whichever comes first)
If that doesnt work then just try your hardest.