Answer
Yes; .5
Work Step by Step
Direct variation has the form y=kx. Thus, we need to simplify to isolate y to see if it is direct variation. Thus, we obtain:
$.7x-1.4y=0 \\\ .7x=1.4y \\\\ y=.5x $
This does have the form y=kx, so it is direct variation. k is the constant of variation, so we know that the thing x is being multiplied by, .5, is the constant of variation.