Question

What is 1.4x-0.4(t-3.1)=5.8 as a decimal?

Answer 1

1.4x - 0.4(t - 3.1) = 5.8

1.4x - 0.4t + 1.24 = 5.8      distributed 0.4 on left side

1.4x - 0.4t           = 3.56    subtracted 1.24 from both sides

This is as far as you can go if they are different variables

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If you typed it wrong and they are supposed to be the same variable, then:

1.4x - 0.4x = 3.56

     1.0x     = 3.56

          x     = 3.56

Answer 2

This took me a bit to complete but this is what i got as an answer so hopefully this helps  also the lines are supposed to go on top of both equations but if helpfull match up the lines on paper (Frist line starts on top of the 2 second line starts on top of the 5)

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$x=0.285714t+3.2571428$ or $t=3.5x -11.4$