Jeff's Housing: Two pairs of statements are given below.

In 1990, Jeff spent $1,000 per month on housing. In 2010, Jeff spent $2,000 per month on housing.

In 1990, Jeff spent 20% of his income on housing. In 2010, Jeff spent 10% of his income on housing.

Calculate Jeff's monthly income in 1990

Calculate Jeff's monthly income in 2010