Answer:

With
representing the slope we have that:


And we are interest on this case the interpretation about the slope and we can conclude that:
For every unit increase in literacy rate (percent of the population that is literate) the age difference (husband minus wife age) falls by 0.0437 units, on average.
Step-by-step explanation:
For this case we have that the regression model adjusted between age difference (husband minus wife age) representing the y variable and literacy rate (percent of the population that is literate) representing the variable x is given by:
where 
And we know that the method used in order to adjust the regression line was least squares.
For this case our dependent variable is y = age difference (husband minus wife age) and the independent variable is x=literacy rate (percent of the population that is literate)
If we compare the regression model adjusted with the linear regression model:

With
representing the slope we have that:


And we are interest on this case the interpretation about the slope and we can conclude that:
For every unit increase in literacy rate (percent of the population that is literate) the age difference (husband minus wife age) falls by 0.0437 units, on average.