We known that PR=QR. Why? Because the two triangles are congruent right triangles, which means that PR and QR are congruent. This means that they have the same length, or PR=QR.

We can substitute the values, 10n+2, and 6n+12, into this equation.

10n+2=6n+12. Subtract 6n from both sides, and 2 from both sides.

4n=10. Now divide by 4 on both sides to solve for n.