Answer:
x= 10
Explanation:
We can use the fact that the sum of all angles in a triangle is 180°.
5x +7x +60 = 180
Solve for x, because we have 1 equation with 1 unknown
5x +7x +60 = 180, combine like terms
12x + 60 = 180. subtract 60 from both sides of the equation
12x + 60 -60 = 180 -60, combine like terms
12x = 120, divide both sides by 12
x = 10