We evaluate b^2 - 4ac.  If the answer is positive, then there are two real solutions.  If it is zero, there is one real solution.  If it is negative, there are 2 complex solutions.  In this equation, a = 1, b = 5, c = 7.  Now we plug in the numbers.
[tex] 5^{2}-4*1*7=1 [/tex]
Because this answer is positive, there are two real solutions.