Which wave has the HIGHEST frequency in ONE second

In part i, the independent variable, the one that is intentionally manipulated, in part ii, the independent variable changes the dependent variable, the one you measure the response in, is the same for parts i and ii. for both parts of the lab, the dependent variable

What is the missing step in this proof ?

Molly shared a spool of ribbon with 12 people. each person received 3 feet of ribbon. which equation can she use to find r, the number of feet of ribbon that her spool originally had?