Answer:
x = 28
Step-by-step explanation:
From the figure attached,
In ΔABC and ΔADC,
AB ≅ AD [Given]
BC ≅ CD [Given]
AC ≅ AC [Reflexive property]
ΔABC ≅ ΔADC [SSS property of congruence]
Therefore, ∠ABC ≅ ∠ADC [CPCTC]
(4x + 13)° = (5x - 15)°
15 + 13 = 5x - 4x
x = 28
