Question 934846
IT=total interest =885
P1=7000 first bond principal amount
P2=? second bond principal amount w/c is the required

from formula 

I=Pin

IT=P1in + P2in
885=7000(.075)(1) +P2(.09)(1)
P2=4000dollars is the answer 

checking I=4000(.09)(1)
I=360 dollars
I=(7000*.075*1)
I=525 dollars
IT=525+360
IT=885 dollars