In the following number-pairs, the second number is obtained by applying certain mathematical operations to the first number. Which numbers should replace X and Y so that the pattern followed by the two numbers on the left side of $::$ is the same as that on the right side of $::$? (NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. $13$ - Operations on $13$ such as adding/subtracting/multiplying etc. to $13$ can be performed. Breaking down $13$ into $1$ and $3$ and then performing mathematical operations on $1$ and $3$ is not allowed.) $X: 65:: 15: Y$