1. baseball + basketball = 240
2. tennisball + soccerball = 500
3. soccerball - basketball + tennisball = 455
4. baseball + tennisball = 215
Subtract 1 from 4
5. tennisball - basketball = -25
Rearrange 3
6. soccerball + tennisball - basketball = 455
Substitute 5 into 6
7. soccerball - 25 = 455
Solve
soccerball = 480
