Answer:Yes, y varies directly with x, and the equation is [tex]y=1.6x[/tex].Step-by-step explanation:To check where there is a direct relationship between x and y, we need to check whether all the x,y pairs we have fit some rule:[tex]y=k\times x[/tex].For the first pair (x=4, y=6.4), [tex]6.4=k\times 4[/tex]Therefore [tex]k = 1.6[/tex].For the second pair (x=7, y=11.2), [tex]11.2=k\times 7[/tex]Therefore [tex]k = 1.6[/tex].For the third pair (x=10, y=16), [tex]16=k\times 10[/tex]Therefore [tex]k = 1.6[/tex].For the second pair (x=13, y=20.8), [tex]20.8=k\times 13[/tex]Therefore [tex]k = 1.6[/tex].So x does directly vary with y, and we have found out that [tex]k=1.6[/tex].