The letters "eleven plus two" are an anagram for twelve plus one.
Negative eleven plus twenty is positive 9.
11+12= 23
13
15x squared plus eleven
64
11
9/11
2 idiot
Five.
⁹/₁₀ + ¹¹/₂₀ =¹⁸/₂₀ + ¹¹/₂₀ =²⁹/₂₀ or 1.45
5