Equality 4 bit with 4 bit by IC 74181 (ALU)
I assume you want to know how to connect an LED to the A=B output so that it is ON when the output is high.

Actually, you've done it wrong for the other 5 outputs as well, since TTL (and LSTTL) does not source current very well, but needs to sink it. So try







simulate this circuit &ndash; Schematic created using CircuitLab

Since you have 6 outputs to monitor, and a 74LS04 has 6 inverters, it's a perfect fit.