Hi!

I'm practicing geometry for my most important math test yet and I came upon this problem I couldn't solve. I tried to solve it for some 90 minutes using triangles and quadrilaterals, but couldn't get the correct answer. β is given and it's 25 degrees. α is the unknown to be solved. The answer in my book is α=70 degrees. What do I need to do to get that answer?

A picture of the figure: imgur: the simple image sharer

The figure is symmetric.

Thanks in advance,

amateur

P.S. English isn't my first language as you may have noticed.