Answer:
d = 6
Step-by-step explanation:
Given the coordinates A(4, 6) and B(d, 12) with the gradient of AB to be 3
Gradient m = y2-y1/x2-x1
Substitute the given values
3 = 12-6/d-4
3 = 6/d-4
Cross multiply
3(d-4) = 6
Expand
3d - 3(4) = 6
3d - 12 = 6
Add 12 to both sides
3d - 12 + 12 = 6 + 12
3d = 18
Divide both sides by 3
3d/3 = 18/3
d = 6
Hence the value of d is 6
