(a) GST amount: $100
(b) GST-exclusive price: $1,000

Working: with GST at 10%, the GST-inclusive price is 11/10 of the exclusive price, so the GST component of a GST-inclusive amount is 1/11 of it.

- GST = $1,100 / 11 = $100
- GST-exclusive price = $1,100 - $100 = $1,000 (check: $1,000 x 10% = $100 GST; $1,000 + $100 = $1,100)