Final answer:
To find out how many friends replied to Josh's birthday party invitations, we can subtract the number of friends who haven't replied (7) from the total number of friends invited (16), which is 9.
Step-by-step explanation:
Josh sent invitations to 16 friends for his birthday party. We know that x friends replied and he is waiting for 7 friends to reply. To find the value of x, which represents the number of friends who replied, we can use the equation 16 (total friends invited) = x (friends who replied) + 7 (friends yet to reply).
Let's solve for x:
16 = x + 7
16 - 7 = x
Therefore, x = 9.
So, 9 friends have replied to Josh's birthday party invitations.