A hydrocarbon X has molar mass 84 but contain no double or triple bonds. Also X has no methyl locant. How many different IUPAC name can be assigned to X?

Molar mass 84 is a multiple of 14 hence, X is based on general formula ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}$ with molar mass 14n. Here, n is 6 and X is ${\mathrm{C}}_6{\mathrm{H}}_{12}.$ As X gas no double bond, it must be a cycloalkane. Cycloalkanes without methyl as locant are