Why would the answer be 3.?

Answer: Cause why not?
Step-by-step explanation:
[tex]3(4x-1)=-2x+19+8x-4[/tex]
First combine like terms:
[tex]3(4x-1)=(-2x+8x)+(19-4)\\\\3(4x-1)=6x+15[/tex]
Now distributive property
[tex](3)(4x)-(3)(1)=6x+15\\12x-3=15+6x[/tex]
Additive Property of Equality
[tex]12x-3+3=15+6x+3\\12x=18+6x[/tex]
Subtractive Property of Equality
[tex]12x-6x=18+6x-6x\\6x=18[/tex]
And finally Division Property of Equality
[tex]\frac{6x}{6} =\frac{18}{6} \\x=3[/tex]