Answer:
x=4
Step-by-step explanation:
72 + 51 + 13x + 5 = 180
128 + 13x = 180
13x = 52
x = 4
The sum of interior angles in a triangle is equal to 180
72 + 51 + 13x + 5 = 180 add like terms
128 + 13x = 180 subtract 128 from both sides
13x = 52 divide both sides by 13
