Can you explain it to me? Specially part A. And please do NOT use work, but Newton's law.

Figure P5.24 25. An object of mass m, hangs from a string that passes over a very light fixed pulley P, as shown in Figure P5.25. The string connects to a second very light pulley P,. A second string passes around this pulley with one end attached to a wall and the other to an object of mass m, on a frictionless, horizontal table. (a) If a, and a, are the accelerations of m, and m., respectively, what is the relation between these accelerations? Find expressions for (b) the tensions in the strings and (c) the accelerations a, and a, in terms of the masses m, and m,, and g. m12 m Figure P5.25