Please, use the {} Code button above the field you're writing your question to make the post be readable.
Also, you should learn about the array concept of Matlab. Your equations look kind of like scalar products, so most likely you can significantly shorten your code and avoid typos this way.
With respect to your question, in this case it's easier to loop with a counter from 1:7, create the respective ta from this and instead of writing data to scalars, save them in arrays. Such as
ta=zeros(1,7);
qe=zeros(1,7);
for cnt=1:7
ta(cnt)=cnt*5+15;
qe(cnt)=...;
...
end
plot(ta,qe)
