If Y Varies Directly as X, Find a Linear Function $$y = 3.6 \text { when } x = 0.9$$

Multiple Choice

If y varies directly as x, find a linear function which relates them.
- $$y = 3.6 \text { when } x = 0.9$$

A) $f ( x ) = 4 x$
B) $f ( x ) = 0.25 x$
C) $f ( x ) = x + 2.7$
D) $f ( x ) = 0.9 x$