Finite State Machine and Robotics
You could do that way, like it's done in software: first you multiply, then you sum. Or you could to all at the same time, with a multiplier chained with the adder.
Of course the logic circuit would be extremely different. In this particular case there isn't a compelling reason to separate the two states: while are you adding the multiplier is idle, and viceversa. There could be a propagation time issue since both the circuits would need to stabilize but it's more of an implementation issue.
A more useful example would be computing
AB+CD
You could do this with:

One adder and one multiplier, in one cycle you do AB, the second CD and in the third one the sum (or even doing the sum in the second cycle), or
Use two multipliers and an adder and do everything in one cycle (timing notwithstanding)

The surface area/number of cell needed in the second case would be almost the double, but it will do the work in half of the time.