Hi! I'm stuck on Chapter 5, 5.4:

"Write a program which asks for a person's favorite number. Have your
program add one to the number, then suggest the result as a bigger and
better favorite number. (Do be tactful about it, though.)".

Any ideas? I'm getting "can't convert fixnum into string" errors.
Here's one of the many things I've tried, er, failed:

puts 'What is your favorite number ?'
num = gets.chomp
better = 'num'.to_i + 1
puts 'This is better: ' + better + '.'

3rd line's getting me. Can't figure out how to add 1 to the response.
Hopefully, I'll figure this out but any tips are welcomed. Thanks!