Which number will be changed to reflect function f across the line y = 5?

Ineed to know the answer to this algebra question.

3x + 4y = 5 x- 3y = -7 solve by substitution

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