Number Test

Study the given pattern carefully and select the number that can replace the question mark (?) in it.
 First row - 15, 11, 43
 Second row - 13, 8, 48
 Third row - 9, 7, ?
 (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)