For the first one, I will solve for t.
s + 2t = 6, first we isolate the t variable,
2t = -s + 6, divide both sides by 2,
t = -s/2 + 3, < There's your answer for 1!
Here's the second one,
3s - 2t = 2, subtract 3s from both sides,
-2t = 2 - 3s, divide both sides by -2,
t = -1 + 3s/2 < There's your second answer!