The equation would be 15x=$60. He would have to save $90 in total to buy the expansion pass. Also the x would be 4 in the equation if you needed it
It really depends on how precise you're going to get.
You could get away with only two parts, but to be really precise, you should probably divide it into twelve (12) parts, because 5/12 means five out of twelve parts, so its would be right on the fifth subdividing marker line.
The answer to question was to question it if you don’t answer your question about how you do that you have a question for you