What is the property of 7+(a+b)=7+a)+b

Due sun 06/03/2019 11: 59 p the list below shows the ages (in years) of 10 people riding in a van to a math competition. calculate the mean age of the people in the van. round your answer to the nearest tenth of s year. 10 12 13 11 10 12 ages 11 38 mean- years ( round your answer to the nearest tenth.) median- years ( enter an exact answer.) hint: textbook measures of center, points possible: 1 license this is attempt 1 of 3. submit