If you have a mixed number f type a b/c, just convert b/c into decimal form.
As b/c is a rational number, it would be either be a limiting decimal or non-limiting but repeating decimal. Round it to the nearest decimal place if desired.
Further, as b/c<0, it will have just 0 to the left of the decimal portion. Now add a towards the left of decimal and you have your result.
For example in 5 3/8, we have 3/8=(3xx125)/(8xx125)=375/1000=0.375
Hence s 3/8=5.375 or 5.38, if you round up to two places of decimals.
In 3 5/7,
5/7=0.714285714285714285714285....,
hence 3 5/7=3.714285714285714285714285.... or 3.7143, rounded up to four places of decimal.