Trigonometry calculator, with the working out

The opposite is about 6.88 cm

1. Label the sides from the angle $35^\circ$: you know the hypotenuse and want the opposite.
2. The opposite and the hypotenuse go together in SOH: $\sin\theta = \dfrac{\text{opposite}}{\text{hypotenuse}}$
3. Substitute: $\sin 35^\circ = \dfrac{x}{12}$
4. Multiply both sides by $12$: $x = 12 \times \sin 35^\circ$
5. Use a calculator (in degrees mode): $\sin 35^\circ \approx 0.5736$
6. $x \approx 6.88 \text{ cm}$ (rounded to 2 decimal places)