Hi Tom,
I probably should have titled the topic "Cascading Equations." The actual survey is REALLY long, but here's a short one demonstrating the problem.
The equations work correctly with small numbers. but starts to fail when the numbers get bigger (q3 >=1000)
Looking at this some more, it seems like has to do with using number_format() on the equations, which I didn't mention originally. The original survey (the long one) is mostly financial/money questions and I wanted to display the equations rounded and with comma-separators.
So when q3 gets to 1000, then the number_format inserts the comma and the 2nd equation is looking at the first one and saying "That's not a number"?
Do you think that is the problem? If so, is there some way to re-cast the string as a number? I tried changing q5 to {number_format(intval(q3) - q4)}, but that didn't help.