A + B + C + D + E + F + G + H + I + J = 76.5
2A - 6B + C + (3/2)D - (1/2)E - F + G + 2H - 50I - 12J = -9
-A - 4B + 11C - 7D + 6E - (3/4)F - 3G - 3H + (1/2)I - (7/2)J = -261.75
32A - B + C + D - 22E +22F - 22G - 7H - I + 3J = -278.5
-(5/4)A + 3B - 5C - 4D + E - (1/2)F + G + 2H + 7I - 44J = 150.5
4A + B - C + D - 6E + 13F - 4G - H + 12I + 8J = 99
9A + 12B + 41C - 200D + 69E - 81F + 11G - 5H - 120I + 500J = -516
-A - 2B - 8C + (20/3)D - E - 12F - 5G - 2H - (2/3)I - 33J = -66 - 2/3
5A - 16B -3C + 3D - 5E - 5F - 7G + 3H - I - 2J = 30
-(1/2)A + B - C + 15D -6E + 7F - 9G + H - 62J = 1
There, try solving that! Wow, that took me 30 minutes just to phrase correctly!
For another problem that is both long AND technically difficult, try solving a quartic function, like this one:
Solve for t: (1/3)t^4 - 12t^3 - 30t^2 - 575t = 53,440,548.
As there is with quadratic functions, there is also a known method for solving quartic problems, but it is exponentially more involved.