Each of the symbols shown above represents exactly one of the digits 0,1,...,9.
In the tableau shown, if the symbols inside the square are considered as two 2-digit numbers, then the symbols below the line represent their sum. In other words:
Moreover, this property should still hold when the tableau is rotated 90 degrees, 180 degrees or 270 degrees. For example, after rotating 90 degrees clockwise we would obtain:
Find the values of the symbols.
SOURCE: Keith Austin (New Scientist)