Question

Redraw everything using Alice’s frame of reference.
Once again, we and our friends, Alice and Bob, are inertial observers who
all meet at a single event. At this event, our clock, Alice’s clock, and Bob’s
clock all read zero and a firecracker explodes. Alice moves to our right at
c/2 and Bob moves to our left at c/2.

Answer 1

in our reference frame

In the Alice reference frame

Velocity of Bob in the Alice reference frame

$$v_B'=\frac{v_A+v_B}{1+\frac{v_Av_B}{c^2}}=\frac{2}{3}c$$