Let's call n the number of days Marika's been training for the race, and 
the distance she runs on the nth day in meters. After the first day, when n = 1, she runs 100 meters, so
On the second day, she runs an additional 4 meters, on the third day, another 4, and so on. Here's what that looks like mathematically:
It would be easier to write this continued addition as multiplication, in which case those same equations would look like
Notice that, in every case, the number 4 is being multiplied by is 1 less than n. We could even write for our first term that 
. In general, we can say that
Which is expressed by option B.
(Bonus: What piece of information from this question did we not need to use here?)
Whats up? What do you need help with
foster can make 42 1/4-pound turkey sandwiches
explanation: 10.5 divided by 1/4 is 42
Note that fiona cannot sell decimal number of cupcakes or muffins. That's why the options A and D are false.
Consider all remaining options:
B. 40 cupcakes and 80 muffins will cost $(40·3+80·2)=$(120+160)=$280, but Fiona Follies sold at least $300 worth of cupcakes and muffins. Thus, this option is false.
C. 60 cupcakes and 70 muffins will cost $(60·3+70·2)=$(180+140)=$320. Now consider expenses. $(60·0.75+70·0.5)=$(45+35)=$80. This option is true.
E. 80 cupcakes and 80 muffins will cost $(80·3+80·2)=$(240+160)=$400. Now consider expenses. $(80·0.75+80·0.5)=$(60+40)=$100 (exactly $100). This option is true.
Answer: correct options are C and E.
