Answer :
First of all we need to convert fractions into decimals or decimals into fractions:
6.4 - y = 6 2/5
6.4 - y = 6.4 / - 6.4 (both sides)
-y = 0 / * (-1) (both sides)
y = 0
6.4 - y = 6 2/5
6.4 - y = 6.4 / - 6.4 (both sides)
-y = 0 / * (-1) (both sides)
y = 0
[tex]6.4 - y = 6 \frac{2}{5} \\\\-y= 6 \frac{2}{5} -6.4\\\\-y= 6 \frac{4}{10} -6.4\\\\-y=0\\\\y=0[/tex]