Plug in 2 for x
f(2) = (2-2) (2+2)
= (0)(4) = 0
f(2) = 0
A dozen eggs is 12 eggs. each one weighs 3.5 grams, so 12 x 3.5 = 42 grams
You've got a nice 66 sitting right in the middle of that left side, so wouldn't it be nice if you could get rid of everything else? Well, with a little division and multiplication, we can!
7 7 6 6 5 5 → (7 ÷ 7) × 66 × (5 ÷ 5) = 1 × 66 × 1 = 66