To set up, add the two interest amounts from each rate. Let x be the amount invested at 15%, and (1-x) be the remaining amount, since the two should add up to 100% which is represented as 1.00.

15%(13000)(x) + 10%(13000)(1-x) = 1900

(.15)(13000)(x) + (.10)(13000)(1-x) = 1900

Now solve this before you scroll down...

1950x + 1300 - 1300x = 1900

650x = 600

x = 12/13 = 92.3%, or $1800 interest

(1-x) = 1/13 = 7.7%, or $100 interest

15%(13000)(x) + 10%(13000)(1-x) = 1900

(.15)(13000)(x) + (.10)(13000)(1-x) = 1900

Now solve this before you scroll down...

1950x + 1300 - 1300x = 1900

650x = 600

x = 12/13 = 92.3%, or $1800 interest

(1-x) = 1/13 = 7.7%, or $100 interest