Interest + interest = total interest 1800*x + 800*(x+0.01) = 190 <<<---=== where x is percentage for $1800 loan expressed as the decimal (like 3.5% = 0.0035 . . . ) 1800x + 800x + 8 = 190 2600x = 190-8 = 182 ====> x == 0.07 = 7%. Answer. $1800 was invested at 7% and $800 was invested at 8%. Check. 1800*0.07 + 800*0.08 = 190 dollars. ! Correct !