Need pls
we use a+b+c equations barely today pls im lost

The  59° .

 
Explanation:

 a + b +  c = 180 .

(in which, "a" , "b", and "c" represent the measurements (in degrees" of each of the THREE (3) angles in a triangle; which always add up to "180 degrees");

Given "a = 65 degrees";  "b = 56 degrees"; Find "c" (the measurement of the "unknown" angle.).

 a + b + c = 180 ;

65 + 56 + c = 180 ;  Solve for "c" .


  180 - (65 + 56)  = c  ;


Note:  65 + 56 = 121 ;

So:  180 - (65 + 56)  = 180 - 121= 59 = c ;  ↔  c = 59 .
 
The  59° .