Step-by-step explanation:
Because 2x and 40° are complementary angles.
[tex] \therefore \: (2x) \degree + 40 \degree = 90 \degree \\ \\ \therefore \: (2x) \degree = 90 \degree - 40 \degree \\ \\ \therefore \: (2x) \degree = 50 \degree \\ \\ \therefore \: 2x = 50 \\ \\ \therefore \: x = \frac{50}{2} \\ \\ \huge \red{ \boxed{ \therefore \: x = 25}}[/tex]
