I don't understand the acceleration equation and not sure how to use Wolfram alpha to solve the matrix

Below is a schematic of a double Atwood machine: a) b) c) d) For each of the masses, draw a free body diagram (3 mark) Write all 4 coupled equations describing the systems (HINT: 3 equations of motion for the 3 masses and | equation relating the accelerations) (4 marks) Write the coupled equations from above into an augmented matrix (2 mark) Using Gaussian elimination to reduce your matrix from part (c) to find expressions for the acceleration of each of the masses and T (in terms of m1, m2 and ms3). To save time, you may use computer software to solve this (e.g. Matlab, Mathematica, Scil.ab, etc), but you must show a screenshot of your code and you must show at least 3 row reduce operations done by hand for full marks. (6 marks)