Question

f(x) = -3/(x+3), if x < -3
f(x) = 2x+9, if x > -3

Calculate the following limits:
a) lim f(x) x->-3-
b) lim f(x) x->-3
c) lim f(x) x->-3+

ive gotten
B) 3
C) DNE

But I cant figure out A (the harder one) do i need the (f(x + h) - f(x))/h for that one? how would I work it out?