Define an operation $ for positive real numbers so that *a* $ *b = ab*/(*a* + *b*).

Then 4 $ (4 $ 4) = what?

In evaluating 4 $ (4 $ 4), we start inside the parentheses, as usual.

So 4 $ (4 $ 4) = 4 $ (16/8) = 4 $ 2 = 8/6 = 4/3.

Define an operation $ for positive real numbers so that *a* $ *b = ab*/(*a* + *b*).

Then 4 $ (4 $ 4) = what?

In evaluating 4 $ (4 $ 4), we start inside the parentheses, as usual.

So 4 $ (4 $ 4) = 4 $ (16/8) = 4 $ 2 = 8/6 = 4/3.