G11 = £30000?
You just put the cell reference... And I suspect you're approaching this from slightly the wrong angle... Do the cells A17 and A18 contain "Yes" and "No" just as a means of getting them in the formula? If so this is not needed...
I'm going to assume that if G11 = £30000 that the required response is "Yes"...
The formula you need in D15 is;
Does that help?