ax²+bx+c=0
The formula to solve for x is:

So for 3x²+13x+10=0, plug in the data
x=-13±√13²-4(3)(10) / 2(3)
x=-13±√169-120 / 6
x=-13±√49 /6
x=-13
±7 / 6
x=-13+7/6
x=-6/6
x=-1
x=-13-7/ 6
x=-20/6 or 3.3repeating
3x²+14x+15=0
x=-14±√14²-4(3)(15) / 2(3)
x=-14±√196-180 /6
x=-14±√16 / 6
x=-14+4/6
x=-10/6 or 1.6repeating
x=-14-4/6
x=-18/6
x=-3