All you can do to this expression is simplify.
You need to combine all "like terms." There are two q terms so you need to combine those. To combine "like terms", simply add their coefficients. 6q has a coefficient of 6 and q has a coefficient of 1. So:

Therefore your end result is:
Need more info, also correct grammar
Arc length = rθ [r = radius of the circle, θ = central angle in radians] ⇒
2π = 8*θ ⇒ θ = 2π/8 = π/4