for equation of form y=mx + b, slope = m and y-intercept is b
for equation y=-2x + 6, m = slope = -2
a line parallel to that line has the same slope,
so the equation of that line so far is
y = -2x + b
since the line passes through (3,1), we can replace x with 3 and y with 1 and solve for b:
1 = -2(3) + b
7 = b
so equation of line is:
y = -2x + 7