There are nine kids in a class. when any two meet, each says "hi" to the other and the answer "hi" follows. before the class starts, how many times would one hear the word "hi"?

Which function has the same domain as y=2x

Fredrick designed an experiment in which he spun a spinner 20 times and recorded the results of each spin

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?