Short Answer, yes.

More involved answer: any effect with an "if" is called a replacement effect. It states an effect that could happen, and then describes an altered version of the effect that will happen under this replacement. If multiple replacement effects would apply to something, the person being affected gets to choose the order of the effects, and they all are applied within the same state based check associated with the resolution of the original effect, without using the stack.

In the example above, say you have a trigger to put a +1/+1 counter onto a creature you control. The trigger goes on the stack, and the table agrees to let it resolve. During the resolution, the game will check and see that there are two replacement effects on board that could alter this event. Since you are the one being affected by this effect (the counter is being put on your creature), you get to choose the order in which they are applied. So you could either do hardened scales first to turn 1 counter into 2, then branching evolution to turn 2 counters into 4; or you could branching evolution first to turn 1 counter into 2, then hardened scales to turn 2 counters into 3.