An investor has $100,000 to invest in three types of bonds: short-term, intermediate, and long term. how much should he invest in each type to satisfy conditions?

short-term pay 4% annually, intermediate pays 6% and long term pays 8%. The investor wishes to have a return of $6700 on his investment, with equal amounts invested in intermediate and long term bonds.

I know it will be an x+y+z system. I don't know how to set it up. x+y+z=100,000; .04x+.06y+.08z=6700 and ? or is it something else?