х dollars - part of 8% per annum ⇒ 0.08x doll. - income
(1000-x) dollars - part of 8% per annum ⇒ 0.09(1000-x) doll. - income
0.08x - 0.09(1000-x) = 84
0.08x - 90 - 0.09x = 84
0.01x = 6
x = 600
$600 - part of 8% per annum
$400 - part of 9% per annum
х dollars - part of 8% per annum ⇒ 0.08x doll. - income
(1000-x) dollars - part of 8% per annum ⇒ 0.09(1000-x) doll. - income
0.08x - 0.09(1000-x) = 84
0.08x - 90 - 0.09x = 84
0.01x = 6
x = 600
$600 - part of 8% per annum
$400 - part of 9% per annum