A: We want to take away all the useless numbers that don’t relate to the notebook first, and subtract them.
75 - 6 = 69
69 - 12 = 57
There, now we have to subtract the amount of money she has when she leaves from the total amount spent right now.
57 - 39 = 18
To get the amount spent on all four notebooks, all you need to do is divide by 4
18 / 4 = $4.50
And that’s your answer!
B: $4.50
