The number of telephone calls N between two cities A and B varies directly as the population P\(_{A}\), P\(_B\) respectively and inversely as the square of the distance D between A and B. Which of the following equations represents this relation?

Find the square root of 170 - 20\(\sqrt{30}\)

If x\(^2\) + 4 = 0, then x ?

What is the number whose logarithm to base 10 is 2.3482?

Five years ago, a father was 3 times as old as his son, now their combined ages amount to 110years. thus, the present age of the father is