Answer:
[tex]20\ green\ cards[/tex]
Step-by-step explanation:
Let
x------> the number of blue cards
y-----> the number of green cards
we know that
[tex]\frac{x}{y}=\frac{2}{5}[/tex]
isolate the variable y
[tex]y=\frac{5}{2}x[/tex] -----> equation A
we have
[tex]x=8\ blue\ cards[/tex]
substitute the value of x in the equation A to find the value of y
[tex]y=\frac{5}{2}(8)=20\ green\ cards[/tex]