Trying to understand the following question regarding forces, answer given?

If you draw out the free body diagram, there are two forces acting on the sled. One is the force due to gravity that acts downward and the other is the normal force that the hill exerts on the sled which is upward perpendicular to the slope of the hill. If you break the force due to gravity into a component that's perpendicular to the slope and one that's parallel to the slope, you'll see that the component that's parallel to the slope is what causes the child and sled to accelerate down the hill. If you look closer at the geometry, it's easy to see how that parallel component is equal to m*g*sin(15).