When calculating with numbers, the handling of brackets is easy: you can always calculate the value inside the brackets: [br][br]   [math]\large 2\cdot (5+4)=2\cdot 9=18.[/math][br] [br]Sometimes the numerical value is unknown. However, excluding the brackets may help in simplifying the expression. Previous examples can also be solved by excluding brackets first:[br][br][math]\Large 2\cdot (5+4)=2\cdot 5 +2\cdot 4 = 10 + 8 =18.[/math][br][br]If we should solve [math] 7 - (5+4)[/math], the result is obtained by solving the inner part of brackets first: [br][br][math]\Large 7 - (5+4)=7-9=-2.[/math][br][br]The same result can be solved without solving the brackets:[br][br][math]\large 7 - (5+4)=7\textcolor{blue}{-}5 \textcolor{blue}{-} 4= -2.[/math][br][br]Below are the rules for those cases where the inner part of the brackets is not computable. Such cases are all where there is an expression within the brackets.[br] [br][br]  [math]\LARGE \begin{eqnarray}[br]\textcolor{blue}{a+(b+c)}&=&\textcolor{blue}{a+b+c}\\[br]\textcolor{blue}{a-(b+c)}&=&\textcolor{blue}{a\textcolor{red}{-}b\textcolor{red}{-}c}\\[br]\textcolor{blue}{a(b+c)}&=&\textcolor{blue}{ab+ac}\\[br]\textcolor{blue}{(a+b)(c+d)}&=&\textcolor{blue}{ac+ad+bc+bd}\\[br]\end{eqnarray}[/math][br][br][br]When brackets are excluded and only single terms are left, the like terms can be combined. The terms are like terms, if they are exactly the same but for number part. or example, in the phrase "banana + orange + banana" bananas can be combined because they are the same thing. The phrase can thus be written in the form of "2 bananas + orange".[br] [br][br]