ANSWER
x = 4; 5x + 1 = 21
EXPLANATION
First, we have to find the value of x using the given equation,
[tex]2x=8[/tex]To do so, divide both sides by 2,
[tex]\begin{gathered} \frac{2x}{2}=\frac{8}{2} \\ \\ x=4 \end{gathered}[/tex]Now, with x = 4, replace it into the expression given to find its value,
[tex]5x+1=5\cdot4+1=20+1=21[/tex]Hence, the value of the expression is 21.