For these kinds of problems, the point-slope formula comes in handy.
The point-slope form (y - y1 = m(x - x1) +b) uses the slope and a point given to find the y-intercept, or in this case, the equation of the line.
First, we plug the known #'s into the equation, then solve.
y - 7 = -7/3( x -0)
y - 7 = -7/3x
+7 +7
y = -7/3x +7
Therefore, the equation of the line is: y = -7/3x + 7
Hope this helps!