Nick has $40 and spends $1.50 each day. bob has only $9 but he gets a daily allowance from which he saves $1.50 each day. in how many days will bob have more money than nick?

Even tho' this problem requires an inequality, let's write equations instead:

Nick's money:  $40 - ($1.50 / day)(x)              where x represents # of days
Bob's Money:   $ 9 + ($1.50 / day)(x)

Equate these two expressions:   40 - 1.50x = 9 + 1.50x

Then 31 = 3.00x, and x = 31/3 = 10 1/3 days

The two boys will have the same amount after 10 1/3 days; after that, Bob will have more (since he continues to receive an allowance and Nick continues to spend the money he already has).