This can be easily set up as a proportion:
[tex] \frac{42}{100} [/tex] = [tex] \frac{210}{n} [/tex], such that 42/100 represents 42 percent and 210 is proportionally equivalent to 42, and n is the missing total number of people surveyed.
After cross-multiplication, the answer is 500 people, because 210 is 42% of 500.
