In a colony of 400 families, 68% take a morning newspaper and 45% take an evening newspaper. Every family takes at least one of the two. How many families take both?

The two shares add to 68 + 45 = 113%. Since every family is counted at least once and the true total is 100%, the extra 13% is exactly the families counted twice, that is the families taking both: 13% of 400 = 52. 92 is 23% of 400, the 68 - 45 gap, which answers nothing here. 272 and 180 are the two groups themselves.