[tex]\text{Use sine:}\\\\sine=\dfrac{opposite}{hypotenuse}\\\\\text{We have}\\\\\theta=68^o\to\sin68^o\approx0.9272\\opposite=17\\hypotenuse=x\\\\\text{Substitute:}\\\\\cos68^o=\dfrac{17}{x}\\\\0.9272=\dfrac{17}{x}\\\\\dfrac{0.9272}{1}=\dfrac{17}{x}\qquad\text{cross multiply}\\\\0.9272x=17\qquad\text{divide both sides by 0.9272}\\\\\dfrac{0.9272x}{0.9272}=\dfrac{17}{0.9272}\\\\x\approx18.3[/tex]
