Indeed, there is one variable "x", but your equation "2x^2+7x+3=0" is a quadratic and quadratic equation has two solutions. 

2x^2+7x+3=0

You can also solve the equation using the quadratic formula:

where a, b, and c are the coefficients of the quadratic equation.

In your case, a=2, b=7, and c=3. Plugging these values into the formula you'll also get the 2 solutions that the solver has provided: 

x1 = -1/3

x2 = -3