Imagine fucntions as little machines that turn one number into another. The numbers that enter are called domain and the numbers that go out are called range. In this excercise we are given the couples of numbers that go in and out of the machine. Like this:
So the range of this function will be all the number going out of the function
What you could do it is. Start adding numbers and once you get close to 6 numbers See if you are close to 51 and switch around the numbers to make it equal 51 hope this helps