Sum of two numbers is 20 difference is 4

Step 1: Establish variables for your numbers. I am going to call them X and Y

Step 2: Establish the information you are given

Given X + Y = 11 (the sum of the numbers is 11) ... Equation 1

Given X - Y = 6 (their difference is 6) .... Equation 2

Step 4: Using one of the equations, get one variable in terms of everything else.

I will use equation 1, and get X in terms of everything else.

X + Y = 11

X + Y - Y = 11 - Y ..... Subtract Y from both sides

Using this information substitute it into equation 2

X - Y = 6 .... Equation 2

(11 - Y) - Y = 6 .... Substitute 11 - Y for the variable X

11 - Y - Y = 6

11 - 6 - 2y = 6 - 6 .... Subtract 6 from both sides

5 - 2Y = 0

5 - 2Y + 2Y = 0 + 2Y .... Add 2Y to both sides

5 = 2Y

We now have a value for Y.

We also know that X - Y = 6

So lets substitute 2.5 into this equation for Y

X - 2.5 = 6

X = 6+2.5

What is the sum of X + Y , 2.5 + 8.5 = 11 ... This is correct (we were told this)

What is the difference between the two 8.5 - 2.5 = 6 ... This is correct (we were told this)

I hope this helps.

Step 2: Establish the information you are given

Given X + Y = 11 (the sum of the numbers is 11) ... Equation 1

Given X - Y = 6 (their difference is 6) .... Equation 2

Step 4: Using one of the equations, get one variable in terms of everything else.

I will use equation 1, and get X in terms of everything else.

X + Y = 11

X + Y - Y = 11 - Y ..... Subtract Y from both sides

**X = 11 - Y**Using this information substitute it into equation 2

X - Y = 6 .... Equation 2

(11 - Y) - Y = 6 .... Substitute 11 - Y for the variable X

11 - Y - Y = 6

11 - 6 - 2y = 6 - 6 .... Subtract 6 from both sides

5 - 2Y = 0

5 - 2Y + 2Y = 0 + 2Y .... Add 2Y to both sides

5 = 2Y

**2.5 = Y**... Divide both sides by 2We now have a value for Y.

**Y = 2.5**We also know that X - Y = 6

So lets substitute 2.5 into this equation for Y

X - 2.5 = 6

X = 6+2.5

**X = 8.5****Now always do a check****Y = 2.5, X = 8.5**What is the sum of X + Y , 2.5 + 8.5 = 11 ... This is correct (we were told this)

What is the difference between the two 8.5 - 2.5 = 6 ... This is correct (we were told this)

I hope this helps.

Let the numbers are x and y

then, x+y = 11...(1)

x-y = 6....(2)

add eq.(1) and eq.(2)

2x = 17

x = 17/2

put the value of x into eq.(1)

17/2 + y = 11

y = 11-17/2

y = 5/2

then, x+y = 11...(1)

x-y = 6....(2)

add eq.(1) and eq.(2)

2x = 17

x = 17/2

put the value of x into eq.(1)

17/2 + y = 11

y = 11-17/2

y = 5/2