This problem has some information which does not pertain to the answer. The sample size of 60 is not important to the answer. (Sample size is a concern when it comes to deciding if the survey results are valid!)
75% of the sample says they're going to college, so assuming that the same proportion of students in the entire school is going to college, you need to find 75% of 900.
900 x .75 = 675, the same as the counselor's determination.
