Question 757302
x = investment at 6% interest.  y = investment at 9% interest

simple interest equation: interest = principle*rate*time(years) 
i = p*r*t

a person plans to invest four times as much in 6% as in 9%
x = 4y

the person wants to earn a total of $825 in interest in 1 year so when we add the interest from both accounts it should equal 825.  

0.06x + 0.09y = 825

Substituting 4y in for x we get
0.06(4y) + 0.09y = 825
0.24y + 0.09y = 825
0.33y = 825
y = 825/0.33 = 2500
x = 4y = 4(2500) = 10000