the expression will need to be subtracted from $310 because it is the total amount of money in Andy's bank account. the other side of the equation will need to have 30w in order calculate the amount of weeks that he takes $30 out of. since we want to know how much money he has left after 8 weeks,, we will need to put 8 where the w in the equation is. all of this in mind,, the expression should look like the following:
30(8) - 310 or (30 x 8) - 310
let me know if you have any further questions
:)