The answers are that the number can equal -4 or 1.
You can find this by setting the number equal to x.
x^2 (The square of a number) + 3x (three times a number) = 4
x^2 + 3x = 4 ---> subtract 4 from each side
x^2 + 3x - 4 = 0
Then you can factor this to find the answers
(x - 4)(x + 1) = 0
Set both equal to 0 and solve.