To calculate the value of 7² - 3², we first need to calculate the squares of 7 and 3.

7² = 7 * 7 = 49 3² = 3 * 3 = 9

Now, we can subtract the square of 3 from the square of 7.

49 - 9 = 40

Therefore, the value of 7² - 3² is 40.