random前面要先定义randomize;

循环错了
改成:
for c:=1 to 10 do;
PS:楼上也是对的

var
q,w,e,r,t:real;
c:shortint;
begin
for c:= to 10 do
begin
randomize;
q:=random(300);
w:=random(300-q);
e:=random(300-q-w);
r:=random(300-q-w-e);
t:=300-q-w-e-r;
writeln(q,' ',w,' ',e,' ',r,' ',t);
end;
readln;
end.