16. Study the graph below:

The co-ordinates of A, B and C are: A (3 , 1) ; B (6 , 2) ; C (12 , 4)

The value of D (not shown) also lies on this line. If D is (15 , a), what is the value of a?

E is another point (not shown) o this line and E is (b , 8).

What is the value of b?

If (p , q) is another point on this same line, write down a relationship (equation) between p and q.

19. Find the missing numbers so that the answer is always 56

a = ? b = ? c = ? d = ? e = ?