Can someone help me with this question?

A question on simultaneous equations gives the two equations 3x+2y = 17 and 5x-4y=21. The question asks you to solve for y. I used the substitution method. So I can save time, I solve for y directly, I get 6/11 while if I solve for x first, I eventually get 1 as the answer for y. Normally whether you solve for either one, you should get the same answer. I tried to use an online calculator to solve the problem but when it solved for y, it got 6/11 then all of a sudden changed to 1 in the following steps. What happened or what did I do wrong.