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`5.5+3t = t-2.5 || -t `

`5.5+2t = -2.5 || -5.5 `

`2t = -8 || :2 `

`x=-4 `

Probe:

`5.5+3*(-4) = (-4)-2.5 `

`5.5-12 = -6.5 `✔✔

`=> L={-4} `