If 6 workers build 2 houses in a month, how many houses will 18 workers build in a month?

We can use ratio and proportion to solve this problem. Let x= no. of houses that 18 workers can build $$ \frac{6}{2}=\frac{18}{x} $$ $$ 6x=36 $$ $$ \frac{6x}{6}=\frac{36}{6} $$ $$ x=6 $$ $$ Answer=\:6\:houses $$