There are $16$ tiles total in a $4\times 4$ grid. The edge tiles include all tiles on the outside border. Since the 4 corner tiles should not be counted, count only the edge tiles that are not corners. On each side of the patio, there are $2$ such tiles between the corners. With $4$ sides, that gives $4\cdot 2=8$ tiles. Therefore, the probability is $\frac{8}{16}=\frac{1}{2}$.

There are 3 blueberry muffins and 5 chocolate muffins, so there are $3+5=8$ muffins total. The probability of choosing a blueberry muffin is the number of blueberry muffins divided by the total number of muffins: $\frac{3}{8}$. Therefore, the correct answer is $\frac{3}{8}$.

If the probability of selecting a red tile is $\frac{3}{5}$, then

Let the total number of tiles be $t$. Since there are 12 red tiles,

Cross-multiply:

So the total number of tiles in the bag is $20$.

The probability of choosing a blue marble is the number of blue marbles divided by the total number of marbles. There are 5 blue marbles and $3+5=8$ total marbles, so the probability is $\frac{5}{8}$. Therefore, the equivalent expression is $\frac{5}{8}$.

There are $4\times 4=16$ total ordered pairs on the graph because each spinner can show 1, 2, 3, or 4. Points on the line $y=x$ have equal coordinates: $(1,1)$, $(2,2)$, $(3,3)$, and $(4,4)$. That is 4 favorable outcomes. Therefore, the probability is $\frac{4}{16}=\frac{1}{4}$.