check the picture below.
now, if the angle at ∡BAE is 70°, her twin over at ∡AED is also 70°.
we know AD = AE, so those two twin sides stemming from vertex A, will make twin angles at the bottom, thus ∡ADE is also 70°, because of her twin.
well, that said, surely you know what ∡DAE is.
