You have an else that has no if to start it off. Your prior if was ended with the end in the line right before the else. Try getting rid of that if that's what you want to do.
for Re1=3000
if x<Re1
f1=mc+cof+((Re1-x)*0.18)-(x*0.18)-(Rh1*0.05);
else
f1=mc+cof-(Re1*0.18)-(Rh1*0.05);
end
end
Of course I hope you realize your for loop will go only once , for a value of Re1 of 3000.
