Let x dollars be the amount invested at 10%, then the amount invested at 14% is 10000-x dollars.
Accumulated interest after one year is 0.10x+0.14(10000-x)=1280.
We can solve for x. 0.10x+1400-0.14x=1280; 120=0.04x, x=120/0.04=12000/4=$3000, the amount invested at 10%.
So the amount invested at 14% is 10000-3000=$7000.