5x/4=20/x<=>5x²=80
x²=16
x=radical din 16=4
[tex] \frac{5x}{4} = \frac{20}{x} [/tex]
[tex]5x \times x = 20 \times 4[/tex]
[tex]5 {x}^{2} = 80[/tex]
[tex] {x}^{2} = 80 \div 5[/tex]
[tex] {x}^{2} = 16[/tex]
[tex]x = \sqrt{16} [/tex]
[tex]x = 4[/tex]
