The sum of two numbers is 30. Their difference is 12. Use substitution to solve a system of equations to solve for the two numbers.

9 and 21

Step-by-step explanation:

setting up the equation

let x and y represent the two numbers

this means that x + y = 30

x - y = 12

using substitution to solve

if x - y = 12, that can be rearranged to x = y + 12.

substitute x = y + 12 into x + y = 30

you get (y + 12) + y = 30

simplify

2y + 12 = 30

2y = 18

y = 9

plug this into the original equation x + y = 30. this would be

x + 9 = 30

x = 21

the numbers are 21 and 9.

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