Opposite number or additive inverse of any number (n) is a number which, if added n is a result of 0, the identity element of addition. The opposite number for n is written as -n. So -7 is opposite to 7. -7 + 7 = 0
To figure this out you need to average the numbers. To average them you add them all up and divide by how many are there. (60+30+20)/3 (90+20)/3 110/3 36
