Question

how do you know what side to work from when doing linear equations

Answer 1

2.9x-5.7>-3-0.1x

Answer 2

Conventionally we put the unknow variable on the left and its answer on the right.
But really you can work both sides at the same time. For example, I'll bring the x terms to the left and the constant terms to the right - reversing the signs when I do:
\[29x+0.1x>+5.7-3\] Now just combine and solve for x.