Question

The sum of two numbers is 78. Their difference is 32. Write a system of equations that describes this situation. Solve by elimination to find the two numbers. x + y = 32 y – x = 78 50 and 24 x – y = 78 x + y = 32 54 and 24 x + y = 78 x – y = 32 55 and 23

Answer 1

The equation:

x + y = 78

x - y = 32

The answers:

x= 55

y = 23

Explanation:

Call the first number (x) and the second number (y). Take is as a given that (x) is larger than (y). One is given the following information:

"The sum of two numbers is 78"

"Their difference is 32"

Rewrite this in numerical terms:

x + y = 78

x - y = 32

The process of elimination is a way of solving a system of equations. First one manipulates one of the equations such that one variable has an inverse coefficient of its like term in the other equation. This step one does not need to be performed, as the coefficients of the term (y) are inverses in the equations. Next, one adds the equations. Then one uses inverse operations to solve for the remaining variable. Finally, one back solves for the value of the eliminated variable by substituting the value of the solved variable into one of the equations, and simplifying.

Add the equations,

x + y = 78

x - y = 32

____________

2x = 110

Inverse operations,

2x = 110

x = 55

Back solve,

x + y = 78

x = 55

55 + y = 78

y = 23

Answer 2

55, 23, x+y =78; x-y =32

Explanation:

-the system of equation

x+y = 78

x-y = 32

-solve by elimination

x-y = 32, add y to both sides

x= y+32

x +y =78, substitute x= y+32

y+32+y = 78, subtract 32 from both sides

y+y = 78-32, combine like terms

2y = 46, divide both sides by 2

y = 23

x +y =78, substitute y = 23

x+ 23 =78, subtract 23 from both sides

x = 78-23, combine like terms

x = 55