(3x + 1/2 ) + ( 7x - 4 1/2 )
3x+7x + 1/2 - 4 1/2
10x -4
Some expressions are:
7 times 4 equals 28
20 plus 8 equals 28
10 plus 18 equals 28
25 plus 3 equals 28
I set this up as an inequality,

. If you take the cubed root of 800, you get the lower bound of the side length, which is 9.2. Then I just worked my way up until I hit the first number that put me over a volume of 800. That number is 9.29, because 9.28 cubed is 799.1 (not high enough) and 9.29 cubed is 801.8. Therefore, the bounds of the sides exist within a conjunction:

. That's the best I could come up with to help on that one. Wasn't sure if there was another method you were taught at school. I just used common sense more than any rule.
Let the number be x. Then 1.25x = 325, or x = 260.
20% less than 260 is 0.80(260) = 208
Step-by-step explanation:
-4x - 28 = -4(x + 7) or 4(-x - 7)
Topic: Algebraic factorization
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