To find the missing number, convert what it says in words to an equation: [tex]15 {x}^{2} = 20x[/tex] Divide both sides by 15: [tex] {x}^{2} = \frac{20}{15} \\ \\ {x}^{2} = \frac{4}{3} [/tex] Take the square root: [tex]x = \sqrt{ \frac{4}{3} } \\ \\ x = \frac{2}{ \sqrt{3} } \\ \\ x = \frac{2 \sqrt{3} }{3} [/tex]