What is the regular expression to extract 123+43 from the String 'What is (123+43)?' in the regular expression extractor of JMeter?

The actual html response contains What is (123+43)? The numbers within the braces vary each time and also the arithmetic operand. So How can I get the whole string within the braces using regex extractor in JMeter?

I used What is /(([^)]+))/ but I am not getting anything.

Also I would like to know how to perform the arithmetic operation in JMeter after extracting the String and assign it to a variable. I tried using JSR233 preprocessor, but I don't know how to send back the result to the next Http Request.