Which calculation should be completed first to solve this story problem? allister bought some sheet music. he bought 6 songs for $0.99 each and 1 book for $16.99. he paid $1.38 in sales tax. he gave the cashier $50. how much change should allister get? a. total cost of all the purchases b. total cost of 6 songs c. sum of the cost of 1 song, the book, and the tax d. the change

A. total cost of all the purchases

You can't calculate the sales tax on the sheet music or the change for $50 he would have received (which requires subtracting the total cost from $50) until you know how much the sheet music cost total.

 The B) and C) options aren't  relevant to the problem. You're trying to find the amount of change he gets after paying the total cost for all the sheet music + the tax on that.