Answer:
[tex]x=15^\circ[/tex]
Step-by-step explanation:
In a right triangle:
[tex]\sin \theta =cos(90^\circ-\theta) $ (Complementary angles)[/tex]
Therefore, given:
[tex]Sin (30 + x) \º = Cos (3x) \º\\30+x+3x=90^\circ\\30+4x=90^\circ\\4x=90^\circ-30^\circ\\4x=60^\circ\\$Divide both sides by 4\\x=15^\circ[/tex]