I think its 1000 numbers because there from 1 to 999 there are 999 numbers, and then you add zero because it is also a whole number.
A real number that cannot be expressed as a ratio of integers.
Slope = rise/run =[y2-y1]/[x2-x1]
1) slope = [90 - 30] / [12 - 4] = 60 / 8 = 15/2
2) slope = [75 - 30] / [10 - 4] = 45 / 6 = 15 / 2
The slopps are equal.