One number is 6 less than another number. Their sum is 50. What is the smaller number?
If x = the larger number and y = the smaller number, then which of the following systems could be used to solve the problem?
x + y = 50 and -x + y = 6
x + y = 50 and x - y = 6
x + y = 50 and x + y = 6
x - y = 50 and x + y = 6