Using expectations theory:

You observe that there is a one$-$year Treasury bond with a yield of $6\mathrm{.}0\%.$ You also assume that rates will increase and that the one$-$year bond will increase by $1\mathrm{.}0\%$ each year. For example, you expect the one$-$year bond in year $2$ will be $7\mathrm{.}0\%$ and $8\mathrm{.}0\%$ in year $3.$

With that information, what do you expect the $3-$year interest rate to be in $\%$ terms?