Answer:
10cm represents $10
2cm represents $2
10cm also represents 1week
For every week Andre checks 10cm, deduct 2cm which represents $2 donation for food bank, and remaining 8cm represents $8 left for his Dad's gift.
in 5weeks, which is 50cm, save $8 per week/ per 8cm = $8 × 5 = $40
in 5weeks, which is 50cm, he donate $2 per week/ per 2cm = $2 × 5= $10