Question 203551
Let x = the amount Walter invested at 7%, then $12,000-x = the amount he invested at 9%.
The interest earned on these two amounts can be expressed (after converting the percentages to their decimal equivalent) as:
(0.07)x+(0.09)($12,000-x) and this sum is $970. So...
0.07x+0.09($12,000-x) = $970 Simplify and solve for x.
0.07x+$1,080-0.09x = $970 Combine the x-terms.
-0.02x+$1,080 = $970 Subtract $1,080 from both sides.
-0.02x = -$110 Divide both sides by -0.02
x = $5,500

Walter invested $5,500 at 7%