Question 1159542
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72

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Workout:

B = G           (1)
3(B-24) = G     (2)

Eq (1) allows us to substitute B for G on RHS of (2):
3(B-24) = B
2B = 72
B = 36  ==> G = 36  and  B+G=72


Check:  3(B-24) = 3(12) = 36 = G  (ok)