I need a clearer understanding of how to solve: Lisa was collecting socks to donate to a homeless shelter. She bought 12 pairs at a discount store. Sandra, her friend, came over and brought her 20 pairs of socks. Her cousin showed up with one-fifth the number of pairs that Sandra bought. After work, Lisa’s mom brought 8 more than three times the number of pairs Lisa started with. How many pairs of socks did Lisa end up with?