First, we need to figure out the amounts of months that Gerald has total, with all of the money. So, we divide 35000 by 1400, this leaves us with 25. So, if he keeps spending 1400 per month, it will last him 25 months, but this is not what the question asks, is it? In 25 months, his inheritance will be fully depleted, in 24 months he will have spent 33,600 dollars, meaning he will have 1400 dollars left (35000 - (24 * 1400))and in 23 months, he will have spent 32,200 dollars, meaning that he will have 2800 dollars.
"In 24 months he will have spent 33,600 dollars, meaning he will have 1400 dollars left 35000 - (24 * 1400)"
35000 - (24 * 1400)
24 months