Solve the following system of simultaneous linear equations by the substitution method:

mx - ny = m² + n²

x + y = 2m

Solve the simultaneous equations 3x - y = 5, 4x - 3y = -1. Hence, find p, if y = px - 3.

Solve the following systems of simultaneous linear equations by the elimination method

3x + 4y = 10

2x - 2y = 2