Answer
Find out the what will their monthly income be .
To proof
Let us assume that the their monthly income be x .
As given
Ronda Rollins gets a Social Security benefit of $350 per month
Her husband receives a benefit equal to 200 percent of Ronda's benefit.
If they take an additional $400 per month from savings .
200% written in the decimal form

Than the equation becomes

x = 350 + 700 + 400
x= $1450
Therefore monthly income be $1450 .
Option (D) is correct .
Hence proved