Question

Write an inequality stating the restrictions on x.

Answer 1

0 < x - 50 < 180 (because the external angle cannot be a zero or a negative and it has to be less than 180 degrees)
0 < 3x < 180 (because an angle of a triangle has to be greater than 0 and less than 180 degrees)

0 < x - 50 < 180
add 50 to both sides
50 < x < 230 --------- (1)

0 < 3x < 180
divide by 3
0 < x < 60 --------- (2)

Combining (1) and (2) we get:
50 < x < 60