Question 525500
Let
She invests at 6% = x
She invests at 7% = 16000-x
Given
Total Amount invested = 16000
Total Annual income = 1080

(Amount invested at 6%) * (6%) + (Amount invested at 7%)( 7%)=Total income  

x*6/100 + (16000-x)*7/100=1080
Multiply by 100 both sides
x*6 + (16000-x)*7=1080*100
6x+112000-7x=108000
-x=108000-112000
-x=-4000
Multiply by -1 both sides
x=4000


She invests at 6% = x = 4000
She invests at 7% = 16000-x = 16000-4000=12000


Check
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4000*6/100 + 12000*7/100=1080
40*6+120+7=1080
240 + 840 = 1080
1080=1080