Whats 9+10?? like i need to know

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

The moats separating people from the animals are 5 m wide for lions and 4 m wide for the elephants. if the lion’s moat is 4 m deep, how deep should the elephants’ moat be?

Use the distributive property -7(-2x+u-2)