We have 7 shout-outs per day.
There are 3 days before break.
Let t be the days before break and S the number of shout-outs before break, we can write a linear relation:
[tex]S=7\cdot t[/tex]Then, if there are 3 days before break, then t = 3 and S will be:
[tex]S=7\cdot3=21[/tex]Answer: he will give a total of 21 shout-outs.