Answer: Yes it is linear
How can we tell? Because it is in the slope intercept form y = mx+b, which is the general template for any linear function.
You may want to rewrite the x/5 as (1/5)x to have the equation y = (1/5)x-sqrt(11)
Compare y = (1/5)x - sqrt(11) with y = mx+b
We see that m = 1/5 is the slope and b = -sqrt(11) is the y intercept
If you were to graph out y = (1/5)x - sqrt(11), you should see a straight line form.