Underlining to show Matching Brackets

Here is the algebraic equation again, this time with the matching parts underlined:

X = [( 2Y + 3) ( Z - 2)] / ( B + A )
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In algebra, expressions are made by combining sub-expressions. In the example, ( 2Y + 3), ( Z - 2), and ( B + A ) are sub-expressions. A larger sub-expression

[( 2Y + 3) ( Z - 2)]

is built up using two of these sub-expressions, as the parentheses and brackets show. The final expression is made by combining the larger sub-expression with the sub-expression ( B + A ). The brackets and parentheses show how this was done. Without brackets and parentheses, the structure of the expression would be lost:

X = 2 Y + 3  Z - 2  /  B + A 

The brackets of QBasic play much the same role.