A think-aloud interview format was tailored based on the Gao et al. study. One researcher conducted all twelve interviews using a semi-structured interview guide and 150 observed interviews completed by experienced group members (on other topics) before starting the interview process in person. Students were provided an iPad and an Apple pencil and asked to draw structures or write out ideas while verbally describing their thought processes in response to the interview prompts. The iPad screen was recorded to capture drawings and audio. Zoom was used as a backup to capture the voice recording when the video capture was 155 turned off. Students were given a packet with each problem and instructed to work the problems in order. Each problem was printed on one page. The researcher did not provide hints or clues regarding how to solve each problem and only moved on to the next question when a student indicated the end of the answer. The researcher reminded the interviewees to draw structures and verbally explain their thought processes in addition to drawing structures.