Ithis identity property of addition or additive inverse property? ?

9x+(-9x)+12=0+12

i see both of the properties but i'm not

Aboard 60 in. long is cut two parts so that the longer piece is 5 times the shorter. what are the length of the two pieces?

Five infinity stones cost $16.80. what is the price per infinity stone ?

Idon't want to fail summer school.the probabilities of contamination in medicine capsules due to the presence of heavy metals and different types of microbes are given in the table.the probability of capsule b having microbial contamination is (the same as, greater than, less than) the probability of capsule d having it.