Book Maths Puzzle Algebra

Solve:
10=t^2-3t

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Book Other Question

Jesus invests some money at 6%, and then invests $5,000 more than twice this amount at 9%. His total income from the two investments is $3,330. How much money did he invest at 9%?

I can figure out a regular simple interest problem, but get lost on problems like this. Help?!?!

Kathy solve 2x^2 - x - 1 = 0