In a triangle we apply angle sum property of triangle, which is given by:
Sum of angles of triangle =180 degrees.
We are given three angles,
A =(4x-13)
B =15
C =(x+18)
Adding the three angles and equating it to 180,

combining like terms



x=32
angle A = 4x-13 = 4(32)-13 = 115 degrees.
angle C = x+18 = 32 +18 = 50 degrees.
Answer : angle A is 115 degrees and Angle C is 50 degrees.