Using the triangle, we can find the angle lengths and using those and trig ratios, find the side lengths. Lets say the top side length is "y".
Using the Law of triangles, we can find the missing angle from 180-90-70=20 deg.
Then we can use the Law of sines,
sin(70)/13=sin(20)/y
y=sin(20)*13/sin(70)
y=15.34
Finally, we use the Pythagorean Theorem, (13)^2+(15.34)^2=x^2
x = 20.1
