The result of 10 + +'20' is 30. The expression is evaluated as follows: first, the unary plus operator (+) is applied to the string '20', converting it to the number 20 (this is similar to Number('20')). Then, the addition operator (+) adds 10 and 20, resulting in 30. This demonstrates how the unary plus can be used for explicit type conversion in an arithmetic context. Without the unary plus, the expression 10 + '20' would result in the string '1020' due to string concatenation.