Which Symbol? : nrich.maths.org

'Which Symbol?' printed from http://nrich.maths.org/

Put in the missing symbols to make these number sentences correct.

Use $+ , -, \times , \div$ and $ =$ .

For example:

Try these:

All these number sentences below, except two of them, have two solutions.
Can you find the symbols to use?

Which two number sentences have only one answer?
Can you see why this is so?

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