passes (2,3)
[tex]3 = a \times {b}^{2} [/tex]
passes (5,24)
[tex]24 = a \times {b}^{5} [/tex]
observe
[tex] {b}^{3} = \frac{a \times {b}^{5} }{a \times {b}^{2} } = \frac{24}{3} = 8 \\ b = 2[/tex]
substitute to first equation we get a=¾
so the equation is
[tex]y = \frac{3}{4} \times {2}^{x} [/tex]