The two numbers are 5 and 16. To arrive to these answers, express the statement question in the form of expressions x+y=21 and x-y=11. Then do x=21-y so that you get the value of x. substitute this value of x in the second expression in order to give you (21-y)-y=11, which then gives 21-2y=11. So 2y=21-11, which gives 2y=10 hence y=5. Then substitute they value of y in the first expression x+y=21 to get the real value of x, x+5=21. So x=21-5=16, therefore, x=16.