Reggie was solving a system of equations. after manipulating them, he decides to add the two equations shown below together to eliminate the variable x. what property justifies this?

6x + 5y = 17
-6x + 2y = 4

please show work :)

thank you to anyone who helps me :)))

The birth weights of newborn babies in the unites states follow in a normal distrubution with a mean of 3.4 kg and standard deviation of 0.6 kg. reaserches interested in studying how. children gain weights decide to take random samples of 100 newborn babies and calculate the sample mean birth weights for each sample