Answer:
x = 18
Step-by-step explanation:
In order for a triangle to be a triangle, all angles must add up to 180.
This means that we can create an equation to solve for x, using the angles given.
180 = 60 + (4x+3) + (2x+9) --> remove brackets and combine like terms
180 = 60 + 6x + 12
180 = 72 + 6x
108 = 6x
18 = x
