Is there a multiplicative inverse b, such as a x b = 1, for each rational number a? explain. please help :(

What is the value of x in the diagram below?

7. if the value of x varies directly with the value of y, and x = 3 when y = 21. what is the valu y, and x = 3 when y = 21. what is the value of x when y = 105?

What is the relationship between all triangles that can be drawn given the same three angles