the cost of 20 pens and 12 pencils is rs . 400 and the cost of 6 pens and 4 pencils is rs . 100 . find the cost of each pen ?
"20 p + 12 q = 400 - - - ( 1 ) 6 p + 4 q = 100 8 p + 8 q = 192 - - - ( 2 ) ( 1 ) - ( 2 ) = > 8 p = 160 = > p = 50 answer : a"
multiply(multiply(const_3, const_4), divide(400, add(20, 4)))