Determine Units Sold for Revenue Increase

Consider a linear equation representing a business's monthly revenue, given by the equation:

$$ R = 1500 + 250x $$

where:

• $R$ is the total revenue in dollars,
• $x$ is the number of units sold.

After a certain promotion, the company expects the revenue to increase by 20% for any given number of units sold.

Write the new revenue equation reflecting this increase and find the number of units $x$ that must be sold to reach a total revenue of $$ 2100 $$.