"At westwood Middleschool, 648 students responded to a survey asking about their favorite type of exercise. Twice as many students chose jogging as swimming. The same number of students chose yoga as jogging. Twice as many students chose biking as jogging. How many students chose each type of exercise?"
Let j = number of joggers, s = number of swimmers, y = number os yogis, b = number of bikers
We are told:
j = 2s
y = j
b = 2j
j + s + y + b = 648
Use the first three equations in the fourth:
j + j/2 + j + 2j = 648 or (9/2)j = 648 hence j = 2*648/9 = 144
Can you take it from here?