Step 1: Resolve forces along the incline.
At equilibrium, the component of gravity along the incline is balanced by the spring force:
\[
mg \sin \theta = k (x - l_0)
\]
where \(x\) is the distance along incline, \(l_0 = 0.8 \, \text{m}\) is natural length of the spring, \(k = 100\sqrt{2} \, \text{N/m}\).
Step 2: Substitute known values.
\[
10 \cdot 10 \cdot \sin 45^\circ = 100\sqrt{2} (x - 0.8)
\]
\[
100 \cdot \frac{\sqrt{2}}{2} = 100\sqrt{2} (x - 0.8)
\]
Step 3: Simplify equation.
\[
50 \sqrt{2} = 100 \sqrt{2} (x - 0.8)
\]
\[
x - 0.8 = \frac{50 \sqrt{2}}{100 \sqrt{2}} = 0.5
\]
Step 4: Solve for \(x\).
\[
x = 0.8 + 0.5 = 1.3 \, \text{m}
\]
Step 5: Verify units and reasoning.
Spring force and component of gravity both in N, distance in meters, equilibrium condition satisfied.
Step 6: Final conclusion.
Hence, the block is located at:
\[
\boxed{1.3 \, \text{m}}
\]