um not really a specific enough question for a good answer, but I'll give it a go
all you have to do is use long division and divide the numerator by the denominator (top by bottom)
most often the result will not be pretty so round appropriately (i recommend tenths or hundredths)
for exampe
25/11
use some handy division skills, and you'll get about 2.27
note that improper fractions mean that the decimal form will always be greater than 1, or less than -1
