#### Answer

a. year $ 2039$, $37$ percent.
b. intersection point $(69,37)$.

#### Work Step by Step

a. From the first equation, we have $y=16+\frac{3}{10}x$. And the second equation gives $y=71-\frac{1}{2}x$. Let $16+\frac{3}{10}x=71-\frac{1}{2}x$; we have $\frac{4}{5}x=55$ and $x\approx69$, which corresponds to year $1970+69=2039$. At $x=69$, we have $y=16+\frac{3}{10}(69)\approx37$ percent.
b. The above results are shown as the intersection point of the two lines in the graph given in the exercise, which is at about $(69,37)$.