Andrea's fish tank holds 30 gallons of water. andrea estimates that every inch of a fish's length requires a gallon of water. she wants to purchase some corydoras that are 2 inches long, angelfish that are 5 inches long, and fancy guppies that are 3 inches long. write an equation for the situation.

x + y + z = 30
2x + 5y + 3z = 300
x + y + z = 100
2x + 5y + 3z = 30

Agroup of student volunteers participates in a study designed to assess several behavioral interventions for improving output in a repetitive task. prior to the beginning of the study, all volunteers unknowingly observed, and their output is measured. at the beginning of the study, prior to any intervention, the volunteers perform the same task under the observation of a study administrator, and their overall output increases. which of the following terms describes this phenomenon? a. simpson's paradox b. hawthorne effect are d. novelty effect d. pygmalion effect e. observer-expectancy effect