Ok, so:
We know that David and Mira pay $1,050 for monthly rent.
So, we want to find how much money do they pay for a year.
For this:
$1,050 * 12months = $12,600. Right?
Now, They rented a new apartment for $675 per month and the cost of moving was $245.
So, they will pay:
$675 * 12months + $245 = $8,345.
Therefore, their savings are:
$12,600 - $8,345 which is $4,255