How to work out the equation of a line in form 'ax + by + c'?

Question

I just don't know how to do it. I've worked out the gradient is 1.4, so I guess is it 1.4x + by +c? The line goes through 8, 2.
Can someone please explain how to do it? A-level maths mock tomorrow :/

Answer 1

y - b = m (x - a)
m = 1.4 = 7/5
(a,b) is (8,2)
y - 2 = (7/5) (x - 8)
y = (7/5)x - 56/5 + 10/5
y = (7/5)x - 46/5
5y = 7x - 46
7x - 5y - 46 = 0