Problem: if x and y are integers , what is the least positive number of 24 x + 21 y ?
Rationale: "24 x + 21 y = 3 ( 8 x + 7 y ) which will be a minimum positive number when 8 x + 7 y = 1 . 8 ( 1 ) + 7 ( - 1 ) = 1 then 3 ( 8 x + 7 y ) can have a minimum positive value of 3 . the answer is a ."
annotated_formula: subtract(24, 21)