The answer is 40°
i will tell you how,
Total angle sum of any triangle is 180°
∠A + ∠B + ∠E = 180°
70° + 80° + ∠E = 180°
solve for ∠E
∠E = 30°
Now solve use ∠BDE,
∠B + ∠D + ∠E = 180°
20° + 90° + 30° + x = 180° (in triangle DEB, ∠E = 30 + x ) (∠D is 90°)
solve for x
there fore, x = 40°