Answer:
[tex]\huge\boxed{g=3}[/tex]
Step-by-step explanation:
[tex](x+7)(x-4)=x^2+gx-28\\\\\text{Use}\ FOIL:\ (a+b)(c+d)=ac+ad+bc+bd\\\\(x+7)(x-4)=(x)(x)+(x)(-4)+(7)(x)+(7)(-4)\\\\=x^2-4x+7x-28=x^2+3x-28\\\\x^2+3x-28=x^2+gx-28\\\\\begin{array}{ccc}x^2&3x&-28\\\downarrow&\downarrow&\downarrow\\x^2&gx&-28\end{array}\Rightarrow g=3[/tex]
