Answer:
Step-by-step explanation:
Two of the angles are just numbers and you add them.
The third is a term and you add it along with the other two.
The total is always 180 for a triangle.
80 + 58 + 5x - 3 = 180
138 + 5x - 3 = 180 Combine on the left
135 + 5x = 180 Subtract 135 from both sides
5x = 180 - 135 Combine the right
5x = 45 Divide by 5
x = 9
