To solve this equation we have to factor.
We are looking for 2 numbers with a sum of -3, and multiplied they have to be -28. These numbers are -7 and 4.
So:
[tex] {x}^{2} - 3x - 28 = 0[/tex]
[tex](x - 7)(x + 4) = 0[/tex]
[tex]x - 7 = 0 \: \: \: \: x + 4 = 0[/tex]
[tex]x = 7 \: \: \: \: x = - 4[/tex]
