How many soulutions doses the system formed by x-y=3 and ax+3a=0 have for a nonzero number a

We have that
x-y=3 > equation 1
and
ax+3a=0> equation 2

we know that

ax+3a=0> a*(x+3)=0
a=0    and (x+3)=0
if a is a nonzero number
then 
only
x+3=0> x=-3

substitute the value of x=-3 in the equation 1
x-y=3> (-3)-y=3> y=-6

the system has one solution> the point (-3,-6)

Answers4.) -1/205.) -1/406.) -55/127.) -3/4