Solution: first draw the feasible region according to the constraint conditions,

Let 3=a+3y,

Convert the maximum value to the intercept on the y axis,

The area corresponding to this problem is a triangle. Draw a chart. These three vertices are (c, c), (c, ten) and (ten, c). The maximum value of 3 is 1 10 and the minimum value is 8, so 3 ∈ [8, 1 10].

So the answer is: [8, 1 10]