We are told that "y varies directly with x", so y = k*x for some fixed constant k.
When x = 6, we have y = 5 pair up with it. Use these two x,y values to find k
y = k*x
5 = k*6
5/6 = k
k = 5/6
This means y = k*x turns into y = (5/6)x
Next up, we plug in x = 5 to get...
y = (5/6)*x
y = (5/6)*(5)
y = (5/6)*(5/1)
y = (5*5)/(6*1)
y = 25/6