1.
1 = 2.5
2 = 5
3 = 7.5
4 = 10
The n represents how many gallons of milk Mr. Yang is purchasing.
F(6) would be 15. This value means it costs $15 for 6 gallons of milk. :))
2.
f(1) = 1.
The Common Difference is 5, since 11 + 5 = 16 and so on and so forth.
The explicit rule is
f(n) = 1n x 5
((If I got anything wrong on here, it would probably be the explicit rule. Sorry if it is incorrect!))