If you type you problem inside a solve() it will rearrange the equation for you.
However, it only solves the problem for the first variable its reaches.
How do you define the subject in the solve() function?
Try typing in
Solve(x-y/2, x+y-3/2) and press = or Enter
You should get the solution to the two simultaneous equations
x - y/2 = 0
x + y = 3/2