Решение 

 

restart; 1; solve({`+`(x, `-`(y)) = 2, `+`(`/`(`*`(675), `*`(y)), `-`(`/`(`*`(621), `*`(x)))) = 4}) 

{x = -`/`(23, 2), y = -`/`(27, 2)}, {x = 27, y = 25} (14.2.1)