Ytdyklly

this my latex code for the equation

begin{equation} nonumber

 q^*_1  =frac{text{number of women who had their second birth in 1971}}{text{number of women who had their first birth in 1970 textbf{-} number of women had their second birth in 1970}}

  end {equation} 

help me to write denominator as given in pic.

A simple way is to use array for the denominator

begin{equation} nonumber

 q^*_1  =frac{text{number of women who had their second birth in 1971}}{

 begin{array}{c}

   text{number of women who had}\

    text{their first birth in 1970} 

 end{array}

 -

 begin{array}{c}

   text{number of women who had}\

    text{their second birth in 1970} 

 end{array}

 }

  end{equation}  

An approach with parbox

documentclass{article}

usepackage{amsmath}

begin{document}





begin{equation} nonumber

 q^*_1  =frac{text{number of women who had their second birth in 1971}}{text{parbox{4.5cm}{centering number of women who had their first birth in 1970}} - text{parbox{4cm}{centering number of women had their second birth in 1970}}}

  end {equation} 



end{document}

Of course the lengths could be different to fit your sizes...

Just to throw in an alternative layman's view

documentclass{standalone}

usepackage{amsmath}

begin{document}huge

$q^*_1 =  text{number of women who had their (} frac {2^{nd}text{ birth in 1971}} {1^{st}text{ birth in 1970}~-~ 2^{nd}text{ birth in 1970}}$)

end{document}

I'd define a suitable notation, avoiding long verbal descriptions. I also added the verbose version, but adding parentheses for clarity.

documentclass{article}

usepackage{amsmath}



begin{document}



Let's denote by $W(n,y)$ the number of women who had their $n$th~birth

in the year~$y$. Then

begin{equation*}

q^*_1 = frac{W(2,1971)}{W(1,1970)-W(2,1970)}

end{equation*}

We can also typeset this with words, but it comes out quite awful

unless we add parentheses

begin{equation*}

q^*_1 =

frac{

  text{number of women who had their second birth in 1971}

}{

  Bigl(

  begin{tabular}{c}

  number of women who had \

  their first birth in 1970

  end{tabular}

  Bigr)

  -

  Bigl(

  begin{tabular}{c}

  number of women who had \

  their second birth in 1970

  end{tabular}

  Bigr)

}

end{equation*}



end{document}

Using equation* avoids the need for nonumber.

Here is a competety different approach using variables instead of the text:

documentclass{article}

usepackage{amsmath}



begin{document}

begin{align*}

  q^*_1  &=frac{A}{B-C}  \

  text{where}~A &= text{number of women who had their second birth in 1971} \

               B &= text{number of women who had their first birth in 1970} \

               C &= text{number of women who had their second birth in 1970} \

end{align*}  

end{document}

For a horizontally centered equation one could use something like the following:

documentclass{article}

usepackage{amsmath}



begin{document}



begin{equation}

  q^*_1  =frac{A}{B-C} nonumber

end{equation} 

begin{align*}

  text{where}~A &= text{number of women who had their second birth in 1971} \

               B &= text{number of women who had their first birth in 1970} \

               C &= text{number of women who had their second birth in 1970} \

end{align*}

end{document}