|Your question doesn't make any sense.|
re: "if cell F43 is less than $150 then it should put 12.75 in the cell"
In what cell should the 12.75 be put?
re: "but if the cell is more than $150 then it should multiply the amount in the cell X 8.75%"
Again: What cell?
re: "but if the cell f43 has a $0 amount then it should put 0 in cell f43"
If F43 has $0 in it, then why would you need a formula to put $0 in it? F43 already has $0 in it.
You need to be more specific regarding what cell has a value in it and what cell should have the formula.
You can't enter values in cell that contains a formula.