Two Numbers with a Sum of 20 and a Difference of 9

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 =  
20 + 9/2

x =  
29/2

x =  14.5
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 =  
20 − 9/2

y =  
11/2

y =  5.5
Therefore, the two Numbers are 14.5 and 5.5
Check Sum of the two Numbers:
11
14.5
5.5
20.0
14.5 + 5.5 = 20 (trailing zero and decimal point are dropped) ✓
Check Difference between the two Numbers:
014
14.5
5.5
9.0
14.5 − 5.5 = 9 (trailing zero and decimal point are dropped) ✓

The solution above and other related solutions were provided by the Find two Numbers given Sum and Difference Application.

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