In general, if you use st r1, M1 then value of r1 will be stored into the memory location M1.
And in case of st r1, (r3) value of r1 stored into memory of r3
here you have st r1, r2(r3) so value of r1 will be stored into memory of (r2+r3)
Correct me if I am wrong.
solved Assembly: st r1, r2(r3) — Isn’t this indexed-memory addressing instruction correct? [closed]