I think you meant [tex]3/4t = 5/8[/tex] you do it like this:
[tex]3/4t = 5/8[/tex]
[tex]4/3 [/tex] multiplied by [tex]3/4t = 5/8 [/tex] multiplied by [tex]4/3[/tex]
Now you multiply the fractions and you should get
[tex]t = 20/24[/tex]
But you can simplify it so your final answer should be
Answer: [tex]t = 5/6[/tex]