Validation confusion

On my web site I have a form that uses JS to perform a math computation.  When validating I get the following error:

  1.. Line 127, Column 43: character "<" is the first character of a delimiter but occurred as data 
  while(num.length - num.indexOf(".") - 1 < ✉ 

  This message may appear in several cases: 

    a.. You tried to include the "<" character in your page: you should escape it as "&lt;" 
    b.. You used an unescaped ampersand "&": this may be valid in some contexts, but it is recommended to use "&amp;", which is always safe. 
    c.. Another possibility is that you forgot to close quotes in a previous tag. 
  2..  Line 127, Column 43: StartTag: invalid element name 
  while(num.length - num.indexOf(".") - 1 < The problem is that you cannot replace a “Math” function “ < “ with “ "&lt;"   a have it do the math.Is there a work around for this issue ?Oliver Snyder