This problem was suggested by a  "Mental Math" challenge from Desmos on Facebook.

 

Clearly those of us with a calculator rather than a brain (how sad) can verify that the answer is  32.

Taking seriously the challenge that this MIGHT be done mentally,  AND recognizing that others may engage differente "mental" processes than you do,  how many different ways can you describe for evaluating the expression?      (You do NOT need to begin your descriptions with "I would not do it this way, but . . .".)

In the Desmos response on Facebook from individuals who did claim to do this mentally, at least 8 different approaches were described.