Task: Question Answering
Input (English): Problem: x , a , z , and b are single digit positive integers . x = 1 / 7 a . z = 1 / 7 b . ( 10 a + b ) – ( 10 x + z ) could not equal 
Options: a ) 30 , b ) 36 , c ) 42 , d ) 63 , e ) 66
Output (English): d