Answer:
B • r = s - 2
Explanation:
Rachel will always be two year younger than Sean. if we substitute the letters with their ages...
[rachel's age] 2 = [ sean's age] 4 - 2
2 = 4 - 2
it can't be A
2 = 4 (two does not equals four)
it can't be C
2 = 4 + 2 (the correct answer is 6, Rachel is not 6 years old)
it can't be D
4 = 2 - 2 (the correct answer is 0. Rachel's not 0 years old as well.
[ also s is the subject in this case. but we are looking for r ]