Question 1125416
You are looking for two equations (two equations are needed to solve for two unknowns).<br>

Let  L=number of lawn seat tickets, and
       C=number of covered pavilion tickets<br>

The first equation comes from the number of concert tickets sold:
  (1)   L + C = 1600<br>

The 2nd equation comes from the total receipts, using the cost per ticket info:   
  (2)  10L + 20C = 22000<br>


There are many ways to solve this system (e.g. matrices, substitution, etc.).  I'll just multiply the first equation by 10 then subtract that result from the bottom equation:
    10L + 20C = 22000
-  (10L + 10C = 16000)
      0L  + 10C = 6000 <br>
C=600 —>  L=1000 (from eq(1))<br>

Ans:  {{{ highlight(  600 ) }}} covered pavilion tickets and
         {{{ highlight(  1000 ) }}} lawn seat tickets were sold