The coordinates of a, b, and c in the diagram are a(p,4), b(6,1), c(9,q). what equation correctly relates p and q?

I don't see any diagram. So, I'll just wing it.

Value of q:
p, 6, 9 ⇒ there is a difference of 3. The sequence increases by 3. So, it can be assumed that the p is equal to 3. A(p,4) ⇒ A(3,4)

Value of q:
4, 1, q ⇒ there is a difference of 3. The sequence decreases by 3. So, it can be assumed that q is equal to -2. C(9,-2)
 
        p        q
A     3        4     ⇒ 3 + 4 = 7
B     6        1     ⇒ 6 + 1 = 7
C     9       -2    ⇒ 9 + (-2) = 7

Notice that the sequence has an equation of p + q = 7.

r   = 2.65m

good luck!

cutie~