SOLUTION: I need help with the following problem...I have NO idea what to do!! Thanks in advance for your help! Roberto invested some money at 6%, and then invested $3000 more than twice

Question 144557: I need help with the following problem...I have NO idea what to do!! Thanks in advance for your help!
Roberto invested some money at 6%, and then invested $3000 more than twice this amount at 10%. His total annual income from the two investments was $4200. How much was invested at 10%?
Answer by checkley77(12844) (Show Source): You can put this solution on YOUR website!
.06x+.10(3,000+2x)=4,200
.06x+300+.20x=4,200
.26x=4,200-300
.26x=3,900
x=3,900/.26
x=$15,000 invested @ 6%.
3,000+2*15,000
3,000+$30,000=$33,000 invested @ 10%.
proof:
.06*15,000+.10*33,000=4,200
900+3,300=4,200
4,200=4,200

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