sorry for not being clear , i'm not good at english.
there is no friction between the plane and the block. the floor and the plane
the movements i think that happen is : block m slides on top of inclinced plane M , inclined plane M has acceleration a(M) reletive to the floor only in x axis.
block m has x and y component . his y component that reletive to the ground equal to the one that reletive to the inclined plane because plane M doesnt have y component.
i chose the left direction to be the positive x d of m and downward to be the positive y axis
mass M right direction is the positive x.