Official answer:
Consider the Venn diagram above with labels N, S, and D for Norway, Sweden, and Denmark, respectively, and variables a through g representing numbers of the 100 tourists visiting these countries.
Since 10% of the tourists visited Norway, Sweden, and Denmark, it follows that g = 0.10(100) = 10.
Also, 28 tourists in the group visited both Norway and Denmark, so d + g = d + 10 = 28, from which d = 18.
Furthermore, 23 tourists in the group visited at least Norway and Sweden, so e + g = e + 10 = 23, from which e = 13.
Since 32 tourists in the group visited only Sweden, b = 32.
It is given that 48% of the tourists or 0.48(100) = 48 visited only two of the countries, from which it follows that d + e + f = 48, so 18 + 13 + f = 48 from which f = 17.
Given that 3 tourists in the group visited only Denmark, c = 3.
The number of the 100 tourists who visited at least Norway is 7 + 13 + 10 + 18 = 48.
The correct answer is 48.The number of the 100 tourists who visited at least Sweden is 13 + 32 + 17 + 10 = 72.
The correct answer is 72.Given that 42% of the 100 tourists visited only one of these countries, a + b + c = 0.42(100) = 42, from which it follows that a + 32 + 3 = 42 and a = 7.
The Venn diagram below shows the values of a through g.