Pls help me. This is a geo quiz and I don’t have a clue what I am doing.

Answer:
x= 43
measure= 142'
Step-by-step explanation:
We know that a triangle has a sum of 190 degrees we have 17' and 21'
add them together = 38
180-38= 142' (2nd part of answer)
3x + 10 = 142
3x= 132
x= 43 (1st part of answer)