re = /\b\d{7}\b(?=(?:(?!\b\d{7}\b).)*incomplete n\/a).*?$/m
str = '1281674 the crescent annandale 02/10/2019 16/10/2019 - 16/11/2019 pending 1281640 city west link rd lilyfield 02/10/2019 16/10/2019 - 16/11/2019 pending 1276160 victoria rd rozelle 25/09/2019 14/10/2019 - 15/10/2019 pending 1331626 31/12/2019 - 31/01/2020 incomplete n/a 1281674 the crescent annandale 02/10/2019 16/10/2019 - 16/11/2019'
subst = ''
result = str.gsub(re, subst)
# Print the result of the substitution
puts result
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html