Answer:
Hi!
Explanation:
Since an isosceles triangle has two sides that are equal, those sides are A and C. To do this problem, you would need to substitute the values in for A=C, which would make it 3x+40=x+50. Bring the variables to one side and you have 2x=10, divide by 2. Your answer would be x=5. To find the value of angle A, you do 3*5=15+40=55. Then you can always check with C, 5+50=55. There you go! Hope I helped good luck! What grade are you in by the way?