Answer:
x = -7, A = 65 degrees
Explanation:
[It is important to know that in any triangle, the sum of all three angles is equal to 180 degrees]
Therefore,
x + 72 + x + 51 + 71 = 180
2x + 194 = 180 [collect like terms]
2x = -14 [subtract 194 from both sides]
x = -7 [divide both sides by 2]
To find A, we substitute the value of x into x + 72:
A = (-7) + 72
A = 65 degrees.
Hope this helps! :D