Adding the two equations
3x + 6y + 3x - 6y = 36+0
6x = 36
x = 6
.
subtracting second equation from first
(3x + 6y ) - (3x-6y) =36 -0
12y = 36
y = 3
.
therefore
x = 6 and y = 3
(6,3)
Answer:

Step-by-step explanation:
Subtract (6x-3y) from (9x+2y):

This can also be seen as:

Distribute the -1 to (6x-3y):

Simplify the parentheses:

Group like terms:

Combine:

This expression can't be further simplified. Therefore, 3x+5y is the answer.
:Done
Remark
The trick here is to realize that you have to find the number both have in order to find the difference. That means you take (effectively) 3/8 and 5/8 to find out how much each of them has. The 8 stands for the 136
Step One
Find the number of stamps Alex has. Remember his ratio is the smaller so he will have 3/8
Alex = 3/8 * 136
Alex = 408/8 = 51
Step 2
Find the number that Freddy has.
The total is 136
<u>Formula</u>
Freddy = Total - Alex
Freddy = 136 - 51
Freddy = 85
<u>Check</u>
Let us see if 5/8 * 136 = 85
5*136/8 = 680 / 8 = 85 So your answers are correct.
Difference
Difference = 85 - 51 = 34 which is how many more stamps Freddy has than Alex.