Hello Mal.
I know this is a late reply, but I hope it helps.
You are correct to reach the summation that 18% have registered 2 weeks in advance but it's important to remember that this 18% is clean and excludes the part of the overlap. SO remember that the 72% (common) has a bit related to "registration 2 weeks in advance".
If we draw a Venn diagram, we will see that
Paid in full =10%
The common part related to "registration 2 weeks in advance" = 72-10 =62
Total registration 2 weeks in advance = 62+18=80
Hope this helps!
I know this is a late reply, but I hope it helps.
You are correct to reach the summation that 18% have registered 2 weeks in advance but it's important to remember that this 18% is clean and excludes the part of the overlap. SO remember that the 72% (common) has a bit related to "registration 2 weeks in advance".
If we draw a Venn diagram, we will see that
Paid in full =10%
The common part related to "registration 2 weeks in advance" = 72-10 =62
Total registration 2 weeks in advance = 62+18=80
Hope this helps!