Let x be the total monthly budget.
Then, amount spent on car = x * 1/6
Amount spent on housing = x * 3/8
Amount spent on entertainment = x * 1/4
Total amount spent = x ( 1/6 + 3/8 + 1/4) = x (4 + 9 + 6)/24 = x * 19/24
Balance amount spent on groceries = x — x * 19/24 = 5/24 x
Now, 5/24 x = $ 250
So, x = 250/5 * 24 = $1200