Respuesta :
Answer:
11 + x = -9
x = -20
Step-by-step explanation:
"The sum of eleven and a number" can be translated to: 11 + x, where 'x' is the unknown number.
[tex]11 + x = -9\\\rule{150}{0.5}\\11 - 11 + x = -9 - 11\\\\\boxed{x = -20}[/tex]
Hope this helps.