The Measure Of An Isosceles Triangle Was 70 Degrees ,what Was The Measure Of The Third Angle?

For the measure of an isosceles triangle to be 70 degrees, you would have to place the triangle on a non-flat surface.  Perhaps you meant that the two angles which comprised the matching pair of angles in the isosceles triangle each measured 70 degrees.  If that is the case, you'd simply double and subtract from 180.  As follows.
Angle 1 = 70 degrees
angle 2 = 70 degrees
angle 3 = x (unknown)

angle 1 + angle 2 + angle 3 = 180 degrees
70 + 70 + x = 180
x = 40

So, assuming I understood your question, the measure of the third angle is 40 degrees.