Well you see, you have 2/8, (fraction) and here is a few others, These are COMMON. 4/16, 2/8, 6/24, etc.... You multiply the denominator and numerator by the same answer. Thats how I think I learned it.
2.8 = [tex]2 \frac{8}{10}[/tex]=2[tex] \frac{4}{5}}[/tex]=14/5. Therefore, 2.8 as a fraction would be [tex]\boxed{{\frac{14}{5}}}}}}}[/tex]. Hoped I helped. :)