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## Main Question or Discussion Point

just revising for gcse's and there always seems to be a question with three unknown denominators and you have to rearrange the equation

they are usually like

1/a+1/b=1/c

make b the subject of the formula

can you explain how to do this

they are usually like

1/a+1/b=1/c

make b the subject of the formula

can you explain how to do this