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We define $a\oplus b = ab + a + b $.
If $3 \oplus 5= 2 \oplus x$, what is the value of $x$?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
Investigate how you can work out what day of the week your birthday will be on next year, and the year after...