Nathan deposited 7/9 of his allowance into his savings account. he spent the remaining amount, or $2.50. how much did nathan deposit into his savings account.

Let us assume that total amount of Nathan's allowance = x
Amount of money deposited by Nathan into his savings account = 7x/9
Remaining amount that Nathan spent = $2.50
Now we have to get to the equation for solving the question asked.
7x/9 + 2.50 = x
7x + (9 * 2.50) = 9x
7x + 22.50 = 9x
22.50 = 9x - 7x
22.50 =2x
x = 22.50/2
   = 11.25
So $11.25 is the total allowance of Nathan.
Then The amount of money deposited by
Nathan in savings account = (7/9) * 11.25
                                           = 78.75/9
                                           = 8.75
So Nathan deposits $8.75 in his savings account.

The solution to the system of equations (-2,2)