Explanation

We have two equations:

x + y = 99 ... (1)

x - y = 9 ... (2)

Add (1) and (2) to eliminate y:

2x = 108

Divide by 2:

x = 54

Now, substitute x into (1) to find y:

54 + y = 99

Subtract 54 from both sides:

y = 45

So, the values are x = 54 and y = 45.