Recently in the united states, there were about 300,000,000 cell phone users. that same year, there were 5.7 x 10 to the 9th power, cell phone users worldwide. about how many times larger was the number of cell phone users worldwide then in the united states

5.7*10^9-300,000,000= 5,400,000,000
5,400,000,000=5.4*10^9
So the cell phone users worldwide is 5.4*10^9 more than the cell phone users in USA.

First, think of what you know. you know that the number t the end of the equation will need to be subtracted because it is the money he lost from buying the lawn mower. and your first two weeks have negative profit, so that tells you that c and d are wrong. now you can plug any of the weeks into a and b to see which one works. i'll start with plugging week 1 into a.this isn't right because it says your answer for week one should be -90.so now we need to try the same thing with b.this one got you the right answer, (sometimes if you only check with one of the weeks multiple will work so you need to check with more of the weeks, but it worked out fine here)this means that b is the correct answer.let me know if you need more clarification. i hope this : )