Can someone explain to me how to do these????

To answer the first statement there - To work out the length of the hypotenuse, you would firstly square the two sides given and add them together (i.e. 3{squared} + 6{squared}) and the sum of this equation (i.e.45) would be equal to the square of the hypotenuse, therefore in order to work out the hypotenuse you must square root this number {square root of 45} and you will find your answer which is roughly equal to 6.7. I hope i have explained this in an understandable way :)