If each of the 7 friends eats at least 3/4 of a pizza, then the minimum total amount of pizza needed is:
7 x 3/4 = 21/4
This means we need at least 21/4 or 5.25 pizzas. However, we can't have a fraction of a pizza, so we need to round up to the next whole number of pizzas.
Therefore, the smallest number of whole pizzas needed for lunch is 6.