I guess some of my concerns were not warranted like if Sarah works. This was given. It was not given if Andrew had a savings account prior to this arrangement.Problem probably means (a = Andrew' salary):
11(a + 525 - 1250) = 8250 ; solve for a.
....and they probably don't know each other!!
Agree BUT ONLY IF they are joint: living together et al.So solve 11(2a + 525 - 1250) = 8250 where a = Andrew's monthly salary.