Let
x ----> kilograms of strawberries that Sheldon picks in the morning
y ---> kilograms of strawberries that Sheldon picks in the afternoon
so
we have that
x=y-1 2/5
x=2 1/4 kg
substitute
2 1/4=y-1 2/5
Convert mixed numbers to an improper fraction
1 2/5=1+2/5=7/5
2 1/4=2+1/4=9/4
substitute
9/4=y-7/5
y=(9/4)+(7/5)
y=(45+28)/20
y=73/20 kg
Adds kilograms in the morning and afternoon
x+y=(9/4)+73/20)
x+y=(45/20)+(73/20)
x+y=118/20 kg
Convert to mixed number
118/20=100/20+18/20=5+18/20=5+9/10=5 9/10 kg
therefore
The answer is 5 9/10 kg