What group of people were the first to formalize addition? Answer the following sums. Once you have completed each question, put your answers in order from smallest to largest it will join together to give you the answer you seek.

C: 6 + (-10) E: -12 + 19 E: -3 + (-4) E: 36 + (-18) H: (-7) + (-8)

H: -8 + 6 I: 9 + (-9) N: (-6) + 10 S: 16 + (-1) T: (-9) + (-9)