Since it is a right triangle you will use the equation
a²+b²=c²
C will always be your longest side on the triangle (the hypotenuse)
A and B will be the two other legs
So it is a matter of guessing and checking by inputting the numbers into their own equations so for example answer choice 1 you would:
7.2²+4.6²= c²
Square them
51.84+21.16=c²
Add them
73=c²
Now that you have that you want to square root both sides
√73=√c²
Square root and square cancel out and it leaves you with
8.544...=c
So you know the first one isn’t it
So just use this to figure out the rest