Is the difference between a rational number and an irrational number always an irrational number ?

Of course!

Step-by-step explanation: I will suck at explaining this. Here's the general idea: A rational number is a number that is the quotient of two integers, or whole numbers. Rational numbers are things like 2, 5, 6, 2.5, 2.25, 6.53465, 1.666666666666666666666666666667; you get the idea. The point is, it can be represented by the fraction of two integers. An irrational number is something that cannot be represented this way. It's the same thing with multiplying an even number by an odd number; it'll always be odd, regardless of what the odd number is. Same with odd - even; it'll always be odd. Point being, there is no rational number that can be subtracted by an irrational number and be rational, or an irrational number that is subtracted by a rational number.

900 degrees

step-by-step explanation: