Write and solve an equation to determine the value of x in each figure

 " x = 21 "  ;   The equation is:  " 3x + 117 = 180 " .


Explanation:


3x + 117 = 180 ;  

(Since:  these 2 angles along a straight line, with values of 
3x" and "117" are supplementary because they both make up all the angles on a straight line; thus they are supplementary angles and add up to 180.

      3x + 117 = 180 ; Solve for "x" ;

Subtract "117" from EACH side of the equation:

      3x + 117 − 117 = 180 − 117 ;

to get:

       3x  =  63 ; 

       Now, divide EACH SIDE of the equation by "3"; to isolate "x" on one side of the equation; and to solve for "x" ;

       3x / 3  =  63 / 3 ;

            x  =  21 .

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