The number of real solutions of

$${x^7} + 5{x^3} + 3x + 1 = 0$$ is equal to ____________.

The probability, that in a randomly selected 3-digit number at least two digits are odd, is :

Let R₁ and R₂ be relations on the set {1, 2, ......., 50} such that

R₁ = {(p, pⁿ) : p is a prime and n $$\ge$$ 0 is an integer} and

R₂ = {(p, pⁿ) : p is a prime and n = 0 or 1}.

Then, the number of elements in R₁ $$-$$ R₂ is _______________.

The number of real solutions of the equation $${e^{4x}} + 4{e^{3x}} - 58{e^{2x}} + 4{e^x} + 1 = 0$$ is ___________.