Question 1154013
Total money = 16000

Let x dollars be invested at 9%. So 16000 - x dollars would be invested at 10%.

Interest on the 1st part = x * 0.09
Interest on the 2nd part = (16000 - x) * 0.1

Total interest = 1510 (given)

i.e. {{{x * 0.09 + (16000 - x) * 0.1 = 1510}}}
expanding
{{{0.09*x + 1600 - 0.1*x = 1510}}}
moving variables and constants to either side of the equation
{{{90 = 0.01*x}}}
i.e {{{x = 9000}}}

Amount invested at 9% = 9000, interest earned = 9000 * 0.09 = 810
Amount invested at 10% = 16000 - 9000 = 7000, interest earned = 7000 * 0.1 = 700

Total interest = 810 + 700 = 1510, check!

Ans:
{{{9000}}} dollars invested at 9%, {{{7000}}} dollars invested at 10%.