After Betty gave Stuart 40% of her marble collection, the number of marbles in Stuart's collection increased to 80. If Betty had 60 marbles, how many marbles did Stuart have initially?
After Betty gave Stuart [PERCENTAGE]% of her marble collection, the number of marbles in Stuart's collection increased to [NUMBER]. If Betty had [NUMBER] marbles, how many marbles did Stuart have initially?
If Betty had 60 marbles, she gave Stuart 40/100*60=<<60/100*40=24>>24 marbles.
Since the number of marbles in Stuart's collection increased to 80 after Betty gave him 24 marbles, the number of marbles he initially had is 80-24=<<80-24=56>>56
#### 56