x = amount invested at 10%
y = amount invested at 9%
x + y = 9192
0.10x = 0.09y + 716.85
we have a equation system
x= 9192-y
we substitute x in the second equation
0.10(9192-y)=0.09y+716.85
919.2-0.10y =0.09y+716.85
we clear y
919.2-716.85=0.09y+0.10y
202.35=0.19y
y=202.35/0.19=1065
then
x=9192-1065=8127
x = amount invested at 10%= 8127
y = amount invested at 9%=