This video shows the method to change a word problem into algebra and to identify rational numbers among a group of numbers. In the first part of the video we take a word problem namely - The product of 9 and seven, less than a number. 9 multiplied by something can be expressed as 9(). The unknown number can be expressed as 'x'. Seven less than a number can be expressed as x - 7, so that the final equation becomes 9(x - 7). In the second part we are given a list of numbers. A rational number can be expressed as a fraction of two integers. All the integers are rational numbers as they can be expressed as the number divided by 1. The decimals which have a finite numbers after the decimal are rational as they can be expressed as the number without the decimal divided by certain number of zeroes after 1. Square roots which are integers, are rational numbers. Improper fractions and fractions are rational numbers as they can be expressed as the ratio of two integers. The decimal numbers having non-repetitive infinite numbers after the decimal are irrational.