Explanation:
since I don't see the options, I can only tell you what it is supposed to be and you need to pick the best fitting option :
the score of the test is simply
the number of correctly answered questions times 3 (as every correctly answered question is with 3 points).
the equation is therefore
y = R(x) = 3x
the independent variable x represents the number of correctly answered questions,
and the dependent variable is y, the test score, because the test score depends on the number of correctly answered questions.
so,
R(25) = 3×25 = 75, meaning 25 correctly answered questions × 3 results in the score of 75.