$x+y=100$ ... (1) $x-y=40$ ... (2)
Several mathematicians have compiled PDFs of past Russian Olympiads (e.g., from St. Petersburg, Moscow, or the All-Russian Olympiad). russian math olympiad problems and solutions pdf
Understanding the structure helps you find the right level of PDF: $x+y=100$
The pinnacle of difficulty, featuring problems that often rival or exceed the difficulty of the IMO. Common Topics Covered: from St. Petersburg
From the given equations, we can solve for $x$ and $y$: