The average number of marbles that Bryan and Adam have is 30.
The average number of marbles that Bryan and Charlie have is 52.
The number of marbles that Adam has is ³₇ as many as Charlie.

1. How many marbles does Bryan have?
2. How many marbles does Adam have?
3. How many marbles does Charlie have?

(a)
Number of marbles that Bryan and Adam has
= 2 x 30
= 60

Number of marbles that Bryan and Charlie has
= 2 x 52
= 104

Number of marbles that Adam has = 3 u
Number of marbles that Charlie has = 7 u

Let the number of Bryan's marbles be B.
Let the number of Adam's marbles be A.
Let the number of Charlie's marbles be C.


B + A = 60
B + 3 u = 60 --- (1)

B + C = 104
B + 7 u = 104 --- (2)

(2) - (1)
(B + 7 u) - (B + 3 u ) = 104 - 60
B + 7 u - B - 3 u = 44
B - B + 7 u - 3 u = 44

4 u = 44

1 u = 44 ÷ 4 = 11

Substitute 1 u = 11 into (1).
B + 3 x 11 = 60
B + 33 = 60
B = 60 - 33 = 27

Number of marbles that Bryan has = 27

(b)
Number of marbles that Adam has
= 3 u
= 3 x 11
= 33

(c)
Number of marbles that Charlie has
= 7 u
= 7 x 11
= 77

Answer(s): (a) 27; (b) 33; (c) 77