The common ratio is the common multiple of consecutive terms, usually denoted as "r" for the common ratio. Mathematically the common ratio is a constant that one finds when any term is divided by the term preceding it, in this case:
the expression is 3(15+7). An word problem could be there are 15 apples and 7 bananas. Someone needs to buy 3 times the amount of those. This is represented by that expression.
