Equations to Solve in Your Head

Equations to solve in your head:

6,751x + 3,249y = 26,751

3,249x + 6,751y = 23,249

Is this a joke? Not if you can multiply the first equation by 6,751 and the second by 3,249 in your head, and not if you use a second, simpler method.

Puzzle provided by Kordemsky: The Moscow Puzzles (Dover)