Just solve in separate steps: one to show intermediate result and another to show the fully solved version.
Hopefully, massai is still interested in an answer after more than 9 years of waiting!
You're about to resurrect a dead thread 🙂
BTW, the use of the "solve" command in your answer is misleading. You should rather use an assignement c:=a*b than using an equation c=a*b which is then solved for c.