Dear expert,
I am able to write the equation.
But can you suggest me is it possible to change the text in times new roman style?
Before you start writing you equations, Format>Fonts, press Modify button and select the category you want to change. You can now set font faces you prefer.
For existing formulas, you must edit them individually. The procedure is the same.
(I took the liberty to retag your question as it specifically addresses the math component and makes no sense in the others Writer, Calc, Impress, Draw and Base).
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In case you need clarification, edit your question (not an answer which is reserved for solutions) or comment the relevant answer.