[tex]\sqrt[]{60}[/tex]
1) Let's sketch this out to better grasp it:
Note that we have parallel sides, on that box, so we can state that these lengths are congruent (same measure) to each other.
2) Since we have a right triangle formed by the ramp and now we have the height, we can make use of the Pythagorean Theorem so that we can find the length "b"
[tex]\begin{gathered} a^2=b^2+c^2 \\ 8^2=b^2+2^2 \\ 64=b^2+4 \\ 64-4=b^2+4-4 \\ 60=b^2 \\ b^2=60 \\ \sqrt[]{b^2}=\sqrt[]{60} \\ b=2\sqrt[]{15}\approx7.746 \end{gathered}[/tex]
As we can see, we had to isolate "b" on one side.
3) Hence, the answer is:
[tex]\sqrt[]{60}[/tex]
