Brackets Inside Brackets

Parentheses can sit inside parentheses. Then you work from the innermost pair outward, like opening a box inside a box. 3 × (2 + (10 - 6)): the innermost package is 10 - 6, which is 4.

That gives 3 × (2 + 4). Now the remaining parentheses hold 2 + 4, which is 6, so the line becomes 3 × 6, and finally 18. Each line removes one layer.

One more thing about how the board writes this: a number placed right against a parenthesis means multiply. The board shows 3 × (2 + 4) as 3(2 + 4), with no dot, and both mean 3 times the package. The innermost pair, the one with no other parentheses inside it, is always safe to work out first.