Let's take the unknown number to be X.
The expression will be:
6 + 4X = 42
Let's find X:
First subtract 6 from both sides
[tex]\begin{gathered} 6-6+4x\text{ = 42 - 6} \\ 4x\text{ = }36 \end{gathered}[/tex]Divide both sides by 4:
[tex]\frac{4x}{4}\text{ = }\frac{36}{4}[/tex][tex]x\text{ = 9}[/tex]ANSWER:
9
