we have that
10x - 4 = 2 ( ? )
I proceed to replace the missing value with the given expression
case a-------------> 5x - 4
then
10x - 4 = 2 (5x-4 )--------> 10x - 4 = 10x-8--------> is not solution
case b-------------> 5x - 2
then
10x - 4 = 2 (5x-2 )--------> 10x - 4 = 10x-4--------> is solution
case c-------------> 10x - 4
then
10x - 4 = 2 (10x - 4 )--------> 10x - 4 = 20x-8--------> is not solution
case d-------------> 10x - 8
then
10x - 4 = 2 (10x - 8 )--------> 10x - 4 = 20x-16--------> is not solution
the answer is the option b) 5x - 2
