Multiply the two numbers on each pair of opposite faces of the cube made from this net. What is the largest of the three products?

In the row 4 2 6 the end squares are opposite: $4\times 6=24$. 3 and 2 are opposite: $3\times 2=6$. 8 and 9 are opposite: $8\times 9=72$. The largest product is 72. (54 multiplies 6 and 9, which share an edge.)