A triangle equals 180° so set up the equation as 58+73+12x+1=180 132+12x=180 (I got 132 by adding 58,73,1) Subtract 132 from both sides You should get 12x=48 Divide both sides by 12 X=4
Its really easy. just look at the middle line. now the sides are only the answers including the square roots. so the line in the middle represents 12. The answer is 12