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Write the matrix of the system, find it's inverse, and use it to solve the system. If the system has an infinite number of solutions, express them in terms of the parameter z.
`{(21x,+,8y,+,53z,=,-68),(-4x,-,5y,-,24z,=,6),(-4x,-,2y,-,12z,=,12):}`
x =
y =
z =
`-4 - 1*z`
`2 - 4*z`
`z`