v=√(GM/r)

If you have a TI graphing calculator, try typing it into the calculator like this:

(6.67*10^-11)*(1.99*10^30)[enter]

[ans]/(1.49*10^11)[enter]

[sqrt][ans][enter]

Solve each part of the equation individually to avoid the calculator getting the order of operations mixed up. Usually that's a result of operator error when typing things in, and entering each part as a separate problem can eliminate those errors. By entering it into a graphing calculator as I wrote it above, my answer came out to 29846.7, which is fairly close to 3x10^4 (30,000).