∠DAB and ∠BAD form a linear pair, so ∠DAB + ∠BAD = 180°
116° + ∠BAD = 180° substituted
∠BAD = 64° subtracted 116° from both sides
ΔABC
∠A + ∠B + ∠C = 180° triangle angle sum theorem
64° + x + 60° = 180° substitution
x + 124° = 180° added like terms
x = 56° subtraction property
Answer: 56°
