We know that Kayla is sending invitations to 20 of her friends for a party, It is safe to assume that she needs an invitation for each friend, then she needs 20 invitations.
We know that there are 12 invitations left to send out (this means that of 20 invitations, there are 12 that she did not send already), then the amount that she already sends is equal to the difference between the total number of invitations and the left ones; this is
<span>If Kyla sent out all her invitations thru mailing and was left out with 12, then there were 8 invitations already mailed. If there were other means she used in sending out like personally visiting her friends and handing over a copy, then invitations already mailed is a number less than 8.</span>
