6*(6+y)
This is an application of the distributive property:
a*(b+c) = a*b + a*c
In your case:
6(6+y) = 6*6 + 6*y = 36 + 6y
For more info on the distributive property, check out:
http://coolmath.com/prealgebra/06-properties/05-properties-distributive-01.htm