Explanation

If $\sin A=\sin B$, then:

A=B+360∘n or A=180∘−B+360∘n, where n ∈ Z

Let’s solve:

Case 1:

60∘+X=60∘⇒X=0∘

Case 2:

$$60^circ + X = 180^circ - 60^circ = 120^circ Rightarrow X = 60^circ$$

Possible values of X:

$$X = 0^circ quad text{or} quad X = 60^circ$$