Tamkeea went to the mall shopping. she spent $28 out of her piggy bank at the mall on a new top for the dance. write what transaction she would have to make to get back to the original amount in her piggy bank.

This is the concept of algebra, we are required to right an expression that Tamkeea will have to make in order to get her original amount back;
Let y be the original amount and x be the amount that remained after she spent $28. The original amount can therefore be recovered using the model given by:
original amount=[amount spent]+[remaining amount]
y=x+28

Two because two of one thing is two.