Two Numbers with a Sum of 29 and a Difference of 11

Define variables:
Let x = larger number and y = smaller number
Resulting system of equations:
x + y = Sum
x − y = Difference
Solve the system of equations for x (larger number):
x =  

Sum + Difference/2

Find x by substituting given Sum and Difference into equation for x and simplify:
x =  
x =  
x =  20
Solve the system of equations for y (smaller number):
y =  

Sum − Difference/2

Find y by substituting given Sum and Difference into equation for y and simplify:
y =  
y =  
y =  9
Therefore, the two Numbers are 20 and 9
Check Sum of the two Numbers:

	2	0
		9
	2	9

20 + 9 = 29 ✓
Check Difference between the two Numbers:

	1	10
	2	0
−		9
	1	1

20 − 9 = 11 ✓