Answer
(a). $18$
(b). $6$
Work Step by Step
Examine the given algorithm, we can find:
(a). Given $x=2,y=3$, we have $x\cdot y\gt0$,
execute the $then\ do\ ... \ end\ do$ statements, we get $y=6,x=3$, thus finally we get $z=x\cdot y=18$
(b). Given $x=1,y=1$, we have $x\cdot y\gt0$,
execute the $then\ do\ ... \ end\ do$ statements, we get $y=3,x=2$, thus finally we get $z=x\cdot y=6$