Answer:
Equation of line is given as y = mx + c, where m is the gradient and c is the y-intercept.
First, rearrange x + 7y = 21 into y = mx + c form.
x + 7y = 21
7y = - x + 21
y = -1/7x + 3
Parallel lines have the same gradient so gradient of line is -1/7.
Equation of line is now y = -1/7x + c.
Substitute (-14,4) into the equation to find c.
4 = -1/7(-14) + c
4 = 2 + c
c = 2
Hence, equation of line is y = -1/7x + 2.