For 9, the only thing similar IS the slope of the hypotenuse because the triangles are along the same line. Unless they're asking for the equation of the line, then that's just using the point slope equation which is:
y = - x + 5
For 10, just multiply 4 and 5 by 4 to get 16 and 20. Then multiply 16 and 20 to get 320.
