The distance formula is given by \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}
Take point A(0, -7) as (x₁, x₂) and point B(8, 8) as (y₁, y₂)
Distance AB = \sqrt{(8-0)^2+(8--7)^2}
Distance AB = \sqrt{8^2+15^2}
Distance AB = \sqrt{289}
Distance AB = 17
The line AB is dilated to A'B' by scale factor of 2, it means the length of the line is multiplied by 2
Distance A'B' = 2 × 17 = 34 units
So, the answer to your question is 34 units