
Joseph A. answered 04/25/13
Stanford Grad for Pre-cal/Trig/Calculus/Algebra/Physics Tutor
Using the formula where a0 is the initial value and an is the 'nth' term, while 'd' is the common difference:
a7 = a0 + (n-1) x d = 6 + (7-1) * x 6 = 6 + 36 = 42
QED