A 4-column table with 3 rows. Column 1 has entries run, do not run, total. Column 2 is labeled lift weights with entries 40, blank, 65. Column 3 is labeled do not lift weights with entries blank, x, blank. Column 4 is labeled total with entries 75, blank, 120.
Can you determine what number x represents from the information given? Explain how you got your answer.

Yes, you can determine the number of people who do not run or lift weights by first finding that 55 people do not lift weights, and that 35 people run, but do not lift weights. Subtracting 35 from 55, you get that 20 people do not do either.