First, determine which of SOH-CAH-TOA you need to use. As this question involves the Hypotenuse and the Opposite side, use Sine. As such, write out the equation as: sin(35) = 12/x. (Let x represent the Hypotenuse value). Next, rearrange the equation to: x = 12/sin(35). To do this, multiply both sides of the equation by x and divide both sides by sin(35).Now, input 12/sin(35) into your calculator to give x = 20.9 to 3 significant figures.