Consider the equation as two separate equations: 5x+3=4x−1 and −(5x+3)=4x−1
Now, solve both equations for x as you normally would. Be careful of the negative in the second equation.
Another way to do it (which is harder in this instance, is to square both sides
|5x+3|=4x−125x2+30x+9=16x2−8x+19x2+38x+8=0x=−38±√115618x=−38±3418x=−19±179x=−29orx=−369x=−29orx=−4
Check both answers in original equation and you will find that one of them is invalid.
So the other one is the answer. :)