Question 864518
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Hi
(7x+6) + 10x  + Z = 180
   17x + 6 + Z = 180
             Z = {{{174-(17x)}}}
Re TY:  Must be 'more to the story'
IF X = Z, yes, Z = 55° 
	Z	X	Y	X + Y + Z
x	174-17x	7X + 6	10X	
1	157	13	10	180
2	140	20	20	180
3	123	27	30	180
4	106	34	40	180
5	89	41	50	180
6	72	48	60	180
7	{{{  highlight_green(55) }}} 	55	70	180