Question

(4,7), (x,19); slope = 3 the pair points lies on the same line with the given slope. Find x

Answer 1

So we are given two points, say P1(4,7), P2(x,19).

Slope is given by 
m=3=(y2-y1)/(x2-x1)=(19-7)/(x-4)
solve for x
3=(19-7)/(x-4)
cross multiply
3(x-4)=12
3x-12=12
3x=12+12=24
x=8