Write an equation for a in the diagram giving reasons. Solve this equation to find the angles a and B giving reasons.
Adjacent angles are supplementary (adds up to 180 degrees). Looking at the bottom left hand angle of the larger parallelogram, you see that the angle is 2a. So, you know that $\displaystyle 4a + 2a = 180$.
Looking at the smaller paralleogram, you see that $\displaystyle B + a = 180$ with the same logic.