Let b be the number of boys and g be the number of girls in the club originally.
From the first sentence, we have the system of equations:
b + 12 = 3(g + 4)
b = 3g + 8
From the second sentence, we have the system of equations:
b - 3 = 7(g - 5)
b = 7g - 32
We can solve for b in terms of g from both systems:
b = 3g + 8
b = 7g - 32
Setting the right-hand sides equal to each other, we get:
3g + 8 = 7g - 32
Solving for g, we get:
4g = 40
g = 10
Substituting g = 10 into either equation for b, we get:
b = 3g + 8 = 38
Therefore, there were originally 38 boys and 10 girls in the club.