From Förberedande kurs i matematik 1

By moving the term in \displaystyle x over to the right-hand side and dividing by \displaystyle 3, the inequality can be rewritten as

\displaystyle y\le 2-\frac{2}{3}x.

Then, we see that the area that we should shade consists of all the points under the straight line

\displaystyle y=2-\frac{2}{3}x.