Lua, 402 344344 312 bytes
344312:
r,p,b,x=string.rep,print,' ','x'function d(s,n)h,l=(n+1)/2,s..b;e=r(l,n)if s=='-'then p(e)elseif s=='='then p(e)p(e)else for f=1,n do if p(s=='/'then p'and(r(b,n-f)..s)elseif s=='+'thenor ps=='+'and(f~=h and r(' ',n-1)..'+'or r('+ ',n))elseif s=='x'thenor p(f<h and r(b,f-1)..x..r(b,n-2*f)..x or f>h and r(b,n-f)..x..r(b,2*f-2-n)..x or r(b,f-1)..x)end end end end
402344:
r,p,b,x=string.rep,print,' ','x'function d(s,n)h=h,l=(n+1)/2;if2,s..b;e=r(l,n)if s=='-'then p(r(s..b,n)e)end;ifelseif s=='='then p(r(s..b,n)e)p(r(s..b,n)e)end;if s=='/'thenelse for i=1f=1,n do if s=='/'then p(r(b,n-if)..s)end end;ifelseif s=='+'then for i=1,n do p(i~=hf~=h and r(' ',n-1)..'+'or r('+ ',n))end end;ifelseif s=='x'then for i=1,n do if i<h then p(f<h and r(b,if-1)..x..r(b,n-2*i2*f)..x)elseif i>hor thenf>h p(and r(b,n-if)..x..r(b,-n+2*i2*f-2-n)..x)else p(or r(b,if-1)..x)end end end end
402 Readable:
r,p,b,x=string.rep,print,' ','x'
function'x'function d(s,n)
h=(n+1)/2;
if2;if s=='-'then
p(r(s..b,n))
end
ifend;if s=='='then
p(r(s..b,n))
p(r(s..b,n))
end
ifend;if s=='/'then
for i=1,n do
p(r(b,n-i)..s)
end
end
ifend;if s=='+'then
for i=1,n do
p(i~=h and r(' ',n-1)..'+'or r('+ ',n))
end
end
ifend;if s=='x'then
for i=1,n do
if i<h then
p(r(b,i-1)..x..r(b,n-2*i)..x)
elseif i>h then
p(r(b,n-i)..x..r(b,-n+2*i-2)..x)
else
p(r(b,i-1)..x)
end
end
end
end
That ended up a bit bigger than intended after getting that x working, but at least I do already know a couple places I can shave off some bytes. This is my first pass though.
Also looks like this is an old challenge. Oops- followed a link from a new challenge that was only about printing pluses. I already went through the work though so I'll leave my answer anyways.
Round 2: 58 90 characters eliminatedreduced and I can still do better. A solid next stepit's now painful to look at even when expanded. :|