Explanation:
first step is to find the gradient of the line which "m" on the equation
gradient formula is y2 - y1 ÷ x2 - x1 = -½ as shown on the picture we substituted those points given
2nd step is to substitute on the equation y=mx+c
m= -½
y= 3 (you can choose any from those given points but in my case I chose point A)
x= -2
c= ? only unknown variable so we can can calculate it
substitute as shown on the picture to get c= 2
therefore our equation of the line will be y= -½x+2