I believe it is corresponding to the value of x in type of situational problem.
21. if Sam's erasers are represented by x, then sari, who has three times more, would be represented by 3x. since you are adding two together to get 28, the equation would be 28=3x+x. Simplify to 28=4x, divide by 4 to isolate x, where x=7. multiply this by 3 to get sari's amount.
You'd times15x25 and you'll gladly get the answer
that would be 48/9 because it would be kittens(48) to puppies(9) then simplified to 16/3.
Expression: x × y = x/2 × 2y
