Roberto invested some money at 7 and then investes 5000 more

Roberto invested some money at 7%, and then investes $5000 more than twice this amount at 11%. His total annual income from the two investments was $3450. How much was invested at 11%?

.07x+.11(2x+5000)=3450
.07x+.22x+550=3450
.29x=3450-550
.29x=2900
x=2900/.29
x=10000 amount invested @ 7%
2*10000+5000=20000+5000=25000 amount invested @ 11%
proof
.07*10000+.11*25000=3450
700+2750=3450
3450=3450